If instead of shipping Bruce with whoever you like in your Twitter-au you'd have to ship him with a character on who everyone in your au would be asking 'WHY HIM/HER AND NOT ANYBODY ELSE!??!', what character would it be?
Actually, Superbat was decided for the AU by popular vote! I made a poll about a month and a half ago bc I couldn't decide who to ship Bruce with since I'm an indecisive multishipper.
It was between: SuperBat, WonderBat, SuperWonderBat, CatBat, BatTalia, BatDent, and single while openly flirting with everyone.
SuperBat won by a pretty decent margin.
However, I think if I were to ship him with anybody to get the reaction you were looking for it would be a toss-up between Harvey and Talia.
For Talia, I think Dick would be the only one with an issue. He'd definitely be "Why her and literally not anyone else." I love the beef he has with her, though I'd make it more jokingly in the Au if I did go that route and eventually have him somewhat warm up to her. Damian and Jason would love it. Damian would absolutely rub it in the rest of his sibling's faces that "I have a living biological mother and father who are still happily in love, sucks to suck for the rest of you losers."
For Harvey. The way I wrote the AU the kids generally love "Uncle Harvey" so the kids wouldn't have too much of a problem. It would probably be the other heroes in JL that are like "Batman wtf why are you DATING one of the rogues. He's a criminal who needs to be locked up." Whereas Batman is either covering his ears and going "La la la la la I can't hear you." or going "I can fix him." Both probably both.