An interesting idea (not my cup of tea, but it's your group), since it plays with some variation.
My confusion is with the virus zombies. If any open wound caused by a virus zombie can cause zombism, any hit on your PCs would likely end with the others killing him/her and burning the corpse, because otherwise your screwed.
End result: The highest PC mortality rate since Hunger Games.
Unless it is a very small chance or there is some treatment?