You really have done a good work on your takes on the Superman rogues. There are interesting and very original ideas than at the same time are really in the coherence of the characters. Not always I agree with you, but I congrat on how you have worked your ideas. Now, considering this, how would you create a list of enemies for Supergirl? In the CW series they practically stolen all of Superman enemies to give Kara something to fight against. Supergirl really lacks of her own rogues gallery.
With a Rogues Gallery you typically want a mix of villains who are physical threats and villains who are mental or ideological threats (and of course some that are both). For Supergirl you need to figure out what her status quo should be, what her long-term goal is, and what kind of themes do you want to explore with her that you can't do with the rest of the Superfamily. Then you can make or revamp Rogues to act as threats, roadblocks, or alternate paths to her goals. Love the idea of Kara forming a lunar colony from Future State and I'd still love a Supergirl run that makes that the focus, her building it and overseeing it. With that in mind here's some (not all of them) of Kara's existing Rogues I'd want to use for such a run:
The Worldkillers
Great fit for Kara to face living embodiments of Krypton's sins, given that she's the one born and raised on Krypton. Kara's idealization and nostalgia of Krypton running up against the rather unpleasant reality of the planet at it's worst adds some thematic weight to their fights. Plus they look cool and aren't connected to anything of Kal's which is a big plus. I would tie one villain of Kal's to them, but I'd also straight up give him to Kara in recompense for doing so. Given their role is destroying/conquering worlds, them showing up to torch Kara's new home on the moon feels like an obvious way to demonstrate how her old home is a threat to her new one.
Reactron
Reactron was badass in the Pre-Flashpoint era. Did a better job of living up to his potential than Metallo ever has, I have to concede that. You'd basically be starting over from scratch with him since I don't think he's reappeared post-Flashpoint, and New Krypton is not one of the stories that got recanonized given the state of Kandor. Think it's worth bringing him back all the same, he's a psycho who hates aliens and enjoys killing them, a simple and straightforward motivation that works. Given Kara in my eyes should be far more cynical about humans than her cousin, Reactron is the villain to trot out for when you want to have Kara see her worst beliefs about human nature confirmed. In my ideal take I'd use him as the one that finally pushes her to bail on Earth and start setting up that moon colony. Afterwards he's the muscle of the human forces who want Kara off of "their" moon.
Simon Tycho
Was this guy meant to be a revamp of Psimon? He sure looks like the Young Justice take on Psimon although maybe that's a coincidence. Anyway he's a pretty clear cut Lex Luthor expy given he's a bald genius with an interest in aliens, but his mutations and powers help differentiate the two. Originally he paid world governments for the right to experiment on any extraterrestrial objects that landed within their borders. Maybe write him as Kara's competitor on the moon, in response to an alien setting up shop on Luna, Tycho gets a ton of discreet funding from governments to set up a humans-only lunar settlement, and also has a hidden goal of sabotaging Kara's colony? Can't imagine there wouldn't be some Earth governments that are nervous about aliens colonizing the moon, what if it was used as the launchpad for an invasion of Earth? Tycho as the pro-human villain who brings some interstellar geopolitics sounds like a fun way to flesh him out into a stronger villain for Kara.
Dollmaker
Pre-Flashpoint Dollmaker was great (New 52 Dollmaker not so much). Guess he needs a new name now since a Batman villain has his old one and those guys take precedence. Modelmaker? Plaything? Putting the name issue aside, I'd write him as the darker side of the outcasts Kara has gathered. Not everyone who was kicked out of their society was undeserving of being a pariah. Some have deep-seeded issues and Dollmaker is one of them, with him eventually taking the role of voice for these more violent members. Pre-Flashpoint his father, the Toyman, basically rejected him and never showed him any affection or attention, and his mother abandoned him after taking him away from his father. Compare how Kara feels ignored and overlooked by Kal and by humanity who more readily accept her cousin and nephew as their heroes and I think you could create interesting stories. Dollmaker is the vengeful side of Kara given free reign, the urge to lash out at a world that neither wants nor welcomes you.
Bizarrogirl
Straightforward as can be, all the other Superfamily members have Bizarros (I'd argue Lex is Steel's), this is Kara's. Plus the Sterling Gates storyline was really great, highly recommend check it out. Maybe use Bizarrogirl as an outcast from Bizarroworld who is unable to fit in with Kara's lunar colony either, and turns against it in anger? Basically if she can't find a home there she doesn't want anyone else to find one either.
As for villains I'd just straight up swipe and give to Kara to be hers exclusively from both Superman's Rogues and others?
Amalak
Another cool Kurt Busiek revamp of a Pre-Crisis Superman Rogue, sadly forgotten after Busiek left, Amalak's home world was conquered by Krypton during an imperial phase. Burning with a hatred for all Kryptonians, Amalak became a bounty hunter and a space pirate. Still could easily fit into Kara's Rogues Gallery in the present day, just make it so the World Killers were the ones responsible for subduing his home planet, makes for a nice way to tie Kara's Rogues together. Amalak getting hired to launch raids on Kara's new home, taking slaves and supplies, seems like an organic way to lay the groundwork for them to meet and face off. I want an alien group adversary (maybe bring back The Circle?) to oppose Kara's colony for accepting alien refugees and runaway, similar to how some human governments would dislike her for taking in their outcasts. Amalak could be their "face" until Kara is able to uncover the identity of his backer.
The Eradicator
Eradicator is the one Rogue of Superman's I mentioned connecting to the Worldkillers, and giving to Kara as her Rogue. Pairing him with Kara makes more sense to me, both of them prefer Krypton over Earth, and feel alienated from Kal because of how he's "gone native". Have Eradicator push Kara to turn her colony into a New Krypton rather than allow it to be something new. Eradicator should be the temptation of toxic nostalgia for Kara, the desire to believe everything was better in the old days, and that Krypton is what she should attempt to recreate. Revisit his ability to "posses"/merge with Kryptonians like he attempted with Kal, he bonds with her after orchestrating events to push her into accepting him, then starts subtly influencing her in ways she's not aware of until she's almost changed completely. Like the Venom symbiote yes, that's what I'm going for.
Dominus
Much as she's tried to suppress it, Kara often harbors jealousy of her cousin, envying his greater degree of comfortability with living amongst humans, and she's jealous of Jon taking over for Kal as the main protector of Earth. Dominus is someone who went mad with jealousy after his own loved one surpassed him to ascend to greater heights of power and responsibility. Connection between the two is obvious, if Kara ever gives in to her darker emotions towards her cousin and nephew, she could end up turning into a villain just like Dominus did. Make him her equivalent to Mxy, the reality warper with petty goals and dreams.
Indigo
Indigo is a character that feels like a natural fit for Kara to interact with in the same way as Lena Luthor is. "Daughter of Brainiac vs. Last Daughter of Krypton" is a natural match-up. I do want to reconfigure Indigo to be a more thematic foe for Kara in terms of revamping her background a bit to service that goal. Brainiac creating a Trojan horse is a great concept, I'd just tie that into his world collecting more. Turns out there are many "Indigos" seeded throughout the universe. When Brainiac finds a civilization that shows potential but isn't yet advanced enough to be worthy of collection, he sends an observation unit to merge with one of the dominant sentient life forms and act as an unknown agent. Via injecting a host with nanomachines, the observation unit can slumber within the host until ready, passing on to offspring the host has or infecting others should the host not reproduce/be killed. These agents are utterly unaware of their true nature until their unconscious programming judges the civilization advanced enough for collection upon which a transformation occurs. Nanomachines in the sentient reshape their body and mind into a combat unit who can summon Brainiac for collection and also sabotage a world's defenses.
I would make this a new Indigo, one from a world that became advanced enough for collection and triggered the nanomachine activation in the host. Indigo's world managed to destroy itself before Brainiac could arrive to collect it, and with the death of the planet Indigo's programming ended and she recovered control of her mind and body. Now she's arrived at Kara's colony in an attempt to make a new life for herself, but she's keeping her past a secret. Indigo fears that were Kara to discover the truth, Kara would exile her due to the risk Indigo still poses of summoning Brainiac, and Indigo isn't willing to leave until she can find a way to "cure" herself of Brainiac's brainwashing. What she wants is access to the Fortress of Solitude where she hopes that by studying Superman's data on Brainiac, as well as access to Kryptonian technology, she can create a virus which will sever Brainiac's controls over the machines inside her and allow her to keep the upgrades without risking a loss of control. Knowing that the directive to observe a civilization until it's advanced enough for collection is still in effect, and fearing what could happen if Kara's colony crosses that threshold, Indigo covertly sabotages the colony's advancement at various points to keep it at a safe level for her while also trying to win Kara's trust.
In terms of themes both Kara and Indigo are defined by their male counterparts. Kara exists in Kal's shadow and struggles to metaphorically be her own person, while Indigo literally belongs to Brainiac and is desperate to safeguard her independence. Focus on that and I think Indigo could be a great Rogue for Kara.
Rogal Zaar
I know everyone hates him but there were some hints of potential, and he's no worse than many other Superman Rogues. Make him the "Doomsday" equivalent to Supergirl, he already looks it in terms of appearance, and the two of them have an interesting tie given she wielded his axe for a while (with said axe feeding on her anger). Rogal was a "hero" of a sort, serving the Circle as their agent, and Kara served as a hero of Earth for a while. Both ultimately grew disillusioned with the ones they had served, both struggle with intense feelings of rage, and Rogal also has been hinted at being tied to House El by blood. Originally I suspect he was going to be Kal's half-brother, but that's not happening anymore. Instead why don't we make him a product of a distant ancestor of the Els, a bastard half-breed that was cast off during Krypton's imperial days, and left behind on a planet to fend for himself until he was discovered by the Circle.
Rogal is a more extreme version of what Kara sees herself as: the forgotten and overlooked El family member. Team Rogal up with Amalak, maybe Rogal is the one who recruits Amalak, and have the two of them work together to destroy everything Kara is attempting to build because of their hatred of Kryptonians, and because a powerful organization desires it and is funding them. Ultimately Amalak finds out about Rogal's heritage and betrays him, causing a blood feud between the two which takes the pressure off of Kara for a while as the two battle it out (while still attacking her individually).
I've got some thoughts on a few others, but just some scattered ideas at most. Kara's got some cool Rogues, and there are Rogues who could make good foils for her, but unless DC can embrace Kara being the one who isn't at home on Earth, I don't know if she'll ever really grow into her own. Likewise her Rogues aren't going to stand out if they're just copying the basic Superman plot only against Supergirl. Optimistically Kara will get something after King's mini is done, either another mini or a spot on a team, and I pray we get to see her interact with some of the Rogues I listed again soon.
