And of course the different editions, notably the way the Sabbat moves in Masquerade from a shadowy unknown threat to a playable supervillain horde to a realpolitik sect not so different from the Camarilla. Groups resembling all three styles appear in Requiem: VII, Belial’s Brood and the Lancea et Sanctum.
What else might you change?
All is for the best in the best of all possible worlds.
The Masquerade collapses. An obvious biggie, and the USP of WOD-alike True Blood. For the Masquerade in the process of collapsing and not something vampires wanted, see Sarah Roark’s After Daylight. A hard one to turn back, as noted, so not to be done lightly.
Other creatures through the lens of Vampire. Werewolves are sullen loners who don’t like to talk about how they got Protean 4 while still alive - maybe one lurks on the fringes of Kindred society, like a less charming George from Being Human. Mages are just learned people with access to some of the powers of Thaumaturgy or Cruac... which is bad enough news.
Kindred: The Embraced. It bends and breaks quite a few Masquerade setting points - it actually sits a bit closer to Blood And Smoke in some ways. But vampires who can act in daylight (if they’re well fed) would be much harder to spot from a human outsider’s perspective.
And finally, one of those one-shot ideas that I’ve had stuck in my head for years:
The Last City, Called Gehenna.
Humanity (including the PCs) has been ruled for decades by the ancient kings and queens of the undead, but now a girl has been born bearing a crescent moon birthmark.
Pitched somewhere between Tarkovsky’s Stalker, The Return Of The King and the story of the Nativity.
(And the none-more-grey palette of the Ridley Scott Apple advert.)