>too lazy to read the links and whatnot
But given that the Wraith of Dracula in Harmony indicated that partaking of Juste''s blood would make him complete, I imagine that a Belmont's blood would function much like a normal human's, only far more potent given the clan's supernatural abilities.
Probably tastes a lot better too. Kinda like victory.
But as for why Drac never has, I guess it has to do with the simple game mechanic that drinking Belmont blood equals a game over. I guess a half-canonized theory would be that perhaps Drac has some modicum of respect for the Belmonts (given their power for being mere humans, but this is entirely dependant on how far down the rotten-spiteful-bastard line Drac's at).