I was actually not going to suggest giving them extra strength, I was going to suggest adding points of automatic Potence and Celerity when they get infected with the virus, or get fortitude when they beome human servants.
Anita's getting stronger can just as easily be represented with the storyteller system, and most of the rest of the mechanics are already fleshed out in the WoD, having different disciplines simulates the fact that no 2 vampire's ever have the same abilities.
Werewolfs, and really any lycanthropes can be easily done with Werewolf the apocolypse's rule set just certain things need to be changed. Just erase the Umbra and auspices and breeds. Almot all of the rest already fits. Keep the gifts, they represent the things they can do, like Richards ability to share blood and health etc.
We don't ever see humans getting tougher, the same amount of damage is fatal now as it was then. Its just that Anita can take more because she is getting a boost as a human servant she hasn't miraculously become tougher on her own, it came from somewhere else. Thats why I don't think the HP system works here. I think the best way to do it is use the chart that white-wolf uses. Everyone has 7 levels of damage, its just that the supernatural can soak the damage that they take. If they were still human the same amount of damage would take them out as any other person, its just there bodies can shrug it off.
hmmm... I think I'll write something up about this, and see what everyone thinks of it.