Ok! So the idea is not all the that fleshed out so I don't have too many specifics ironed out, but basically it's a superhero/supervillain AU, with the classic setup of legal heroes who work for the government, illegal vigilantes whose do-gooding is for the people and not government sanctioned, and villains who cause havoc for there own reasons. The heroes might or might not be corrupt, haven't really thought about it, but I know that the hero committee (the bureaucrats and politicians in charge of the heroes) definitely is corrupt.
Basically it focuses on Tommy, Tubbo and Ranboo (they are called bench trio, right?) Plus Mumbo.
The kids are all in foster care, though the how of it is something I haven't fully given thought to beyond Ranboo. I think that Tubbo's father is the supervillain Schlatt and because of that he got seized by CPS and Tommy has just straight up never met his parents, though I have not figured out why that is.
Ranboo had a good relationship with his parents (this is for balance in the trio, as one hates their parents, one loves their parents, and one never knew them. Also, it's for angst) but then Ranboo's parents died and so Ranboo was sent into the foster system.
Now, after a few years in the system Ranboo gets adopted by Mumbo, an old family friend who is also his godfather. Mumbo didn't take him in immediately because he wasn't financially stable but now Mumbo has a cushy job as an engineer (or accountant, haven't decided) at hero tower (he is not a hero himself) and has more than enough money to care for Ranboo. Then Ranboo mentions that he has these two friends from the system and Mumbo just sighs and takes them in as well.
This makes his life hell as he is now saddled with one of the most chaotic trio of children to care for, and to top it all off, the three decide to become vigilantes. I don't know what their powers are beyond the classic Ranboo can teleport and Tubbo can blow stuff up, but I am not sure if that would be what I want.
Either way, Tubbo, Tommy and Ranboo have powers and they decide to become vigilantes to help people because for some reason they don't become heroes. That's either because they are too poor to get in a training program, too weak to be considered for a position, not let in because of their criminal record (Tommy)(it's just petty theft, still rules him out as heroes have to have clean records), not let in because they are the son of a villain (Tubbo) or they have some grudge against the heroes and conscientiously choose not to join them. (Maybe they know of the bad stuff the committee is up to, or maybe they live in the poorer areas and everyone in the poorer areas hates the heroes for never patrolling there. Possibly Tommy has some grudge against the heroes for not saving him from a bad time in his life (unsure) and maybe when the heroes raided Tubbo's home to take down Schlatt they did something to piss him off, though I don't know as I want Tubbo to consider the day he got away from his father to be the best day of his life.
This decision to become vigilantes is done under Mumbo's nose as he works at the hero tower but he figures it out anyways because these idiots are not as subtle as they think they are. Mumbo doesn't turn the three in to his employers as he doesn't want them to go to jail for being dumb kids and instead tails the three while they patrol and cleans up their messes so they don't get caught or seriously injured. Mumbo can shapeshift, but I wouldn't call him a vigilante in this story, he's just the worried, overworked guardian who is constantly being stressed out by the kids who are his responsibility.
Luckily for Mumbo, he has his two best friends in all the world to support him! Grian and Scar! Unlucky for him they are secretly not civilians. Mumbo does not know this, and trusts them, but still doesn't tell them about the three being vigilantes for obvious reasons.
Of course, Mumbo is not as subtle as he thinks he is, and Grian figures it out, but Scar doesn't.
Grian is a villain, part of the dastardly trio known as the Villies, consisting of Big Bad Wolf (Pearl), Stepmother (Gem) and Rumplestiltskin (Grian). He likes to cause chaos and havoc with the goal of toppling hero tower and having it land on everyone in it in revenge for... something... I dunno, maybe he's related to Tommy and they kidnapped him or something.
Scar is a hero, part of the renowned group known as the Cabin Crew, consisting of Logger (Bdubs), Creature (Scott), Survivalist (Etho) and Hunter(who is also called Hot Guy as that is the name he went by prior to joining the Cabin Crew and being rebranded) (Scar). Note that Scar and Bdubs are brothers, Etho is their father, Cleo (who is either a full civilian or ex-vigilante) is their mom and Scott is their uncle (in the case of a family friend you call uncle despite not being related to them. Either way, he's from Cleo's side of the family). Cleo and Etho are divorced.
Despite the fact that neither Grian or Scar are subtle about their career paths, no one in their friend group knows and it's actually kinda insane.
I'm not sure what the story would be like, mostly family drama in the Jumbo household, but I don't know who the main antagonist would be or how things play out.
This is beautiful, and you should continue it. Though it's be funny if Grian specifically was more of an anti-hero, I feel as if it fits better. But you do you! I would love to know what happens-