Street Fighter V's F.A.N.G. concept was actually based on a character planned for a cancelled Darkstalkers

[Nat]

『F.A.N.Gさまのコンセプトは、実は没になった新生◯ァ◯◯◯◯の◯ス◯◯というキャラだったのは秘密中の秘密』
"The secret of secrets is that F.A.N.G’s concept was actually of a character named "XXsuXXXX"¹ in the aborted NEW VAMPIRE"

Translated from the image above.

Most have assumed a new Darkstalkers was in development at some point and this appears to be confirmation of such from Takayuki Nakayama.