Okay so for the swap AU, for ghost and how they're swapped with Hornet, I think it'll be really damn cute (but out of character) for Ghost to just go like: "okay I can't keep fighting you your a small baby sib :(" and than just holding the cinnamon roll that is small hollow, I personally love that but I can understand why you might stray away from it in order to not change the characters too much
I actually find it really funny that you mention that, because I had originally meant for Ghost to be a very interactive and helpful big sib to itty bitty Hollow! This was very early in the concepts for the AU, even back when I first drew something for it and knew little to nothing about Hollow Knight itself.
The idea honestly still pops around in my head every so often, and I find myself questioning whether it's a good idea or not.
From what I know, Ghost/The Knight doesn't really have a canonical personality, the fandom has just given them one (or many). And I don't think it'd be too out of character for Ghost to be at least a little more sympathetic until Hollow is good enough at fighting to actually prove themself worthy.
So instead of a first fight with Ghost taking the fight seriously, it's more like.. a play fight, to get Hollow warmed up with combat, before the real fight really begins in Kingdom's Edge (or whatever that'll become later on).
Still bouncing around the idea, though, because I have many different hc personalities for Ghost, and have yet to decide which one they'll have for this AU.
But anyway, this ask inspired me to draw something as well, so here!