Originally Posted by Prometheus
The only other alternative would for the PCs to very slowly (but clear degenerately) zombify or fall into some sort of coma. Then there is some sort of rumor about a cure that they PCs are allured to
I'd caution against that even more than against just turning them Necropolitan or something. If the PCs are comatose for the rest of the adventure, then they might as well be dead for all their players care. In effect, you've only managed to accomplish one thing by upgrading their conditions: You've made the risk of death less present, as there's always the chance they can be saved if they get bit.
You also throw in a few things that are dangerous to the setting as a whole. You've got a big, glaring continuity error: Why does this guy get to go comatose when everyone else goes zombie? You've also introduced the concept of a cure very early in the game. That shifts the focus from "survive" to "find the MacGuffin"--which is a viable option, but the OP probably wants to focus on "survive" until the PCs are strong enough that it's no longer a challenge.