Glad to know you are thinking on it. Maybe add some hidden dialogues too, because a New Game Plus might become boring if it's just the same thing.
Honestly, IMO, the best thing to do for full NG+ support is to allow for players to win every fight that the plot mandates you lose, and unlock an alternate ending or something.
Depending on how strong Dealer is, maybe NG+ Vampire Mila could ACTUALLY beat what Dorian wants out of him? But hey, you don't have to. It can just be "start the game again with big stats and ignore the canon inconsistency"
This is actually one of the things I dislike about the idea of a NG+. this seems more going into an AU where Mila is more prepared for the battles she faces. I mean, the sheer amount of content to be added with this addition would be more like creating an entirely new game. right from the start, winning the scripted "Vampire" fight in the woods (Chapter 2) would change the games canon. For spoiler reasons, I won't delve into all the scenes that would be changed but there's way too many to put here anyways.