We were introduced with objective modes in Infection with Safe Havens, which as we know failed. I would like to propose 1 Flag Infection which I reckon could actually work.
Humans would have to capture the flag x times in a round to win.
If all the humans die the zombies win.
If the timer expires the zombies win.
When a flag is captured all the remaining humans will score a point. Zombies will score points for infecting the humans as normal.
Proposed scoring system
10 points for flag capture for all remaining humans.
1 point per kill for humans.
3 point per kill for humans that kill a zombie within 20 meters of the flag carrier.
5 points per kill for zombies.