Left 4 Dead enhancements

or how would I design a survival horror zombie game...

I was wondering if there would be say a zombie game where there would be several human players like Left 4 Dead against the zombie hordes. However in this game, when one takes a certain amount of damage, the human player will get infected and turn into a zombie. The other human players remaining would then have to decide to kill their comrade, leave that person behind or try and find a rare cure in the level- usually guarded by a boss zombie.

The infected human as long as he isn't a zombie yet, can still act and work with the remaining human players. However, if the infection timer runs out, the infected human now must turn against his still human friends or else the game will kick him out or at least the AI will take control and force him to attack. Should the zombie be killed, he respawns as another regular zombie that is forced to mindlessly charge at his former comrades.

For more of the survival horror experience, resources are very limited. The human players need food for their stamina – the ability to run and their aim accuracy. Without food, the player cannot run nor shoot very accurately at long range. The humans also need medical kits should they be damaged and to prevent getting into the health where they can be infected. They also carry limited ammo for their heavy rifles, shotguns and machine guns. They also carry a limited amount of clips for their pistols however all ammo can be shared by all members of the team.

The game also includes NPCs where they are infected or hurt. Choosing to help these individuals will reward them with an extra AI driven character that aids them at the risk of that extra character using their own food and ammo stores. Helping these individuals won't also be easy as they usually trigger a zombie swarm to attack. Killing these individuals would yield a small amount of food, medical kits and ammo at the expense of other NPC humans being wary and firing upon the human players. I believe that this sort of experience would yield to a far more realistic (or at least movielike) experience to zombie survival games unlike the more shoot em up Left 4 Dead.