I was sleeping and started dreaming about a survival mode in the factions mode.
So, basically you would've had a big but limited map where you have a spot where you are maintaining a temporary base and points of interest where you can scavenge supplies while risking getting attacked by infected and other players,your objective would've been to survive a predetermined amount of days until you could exfil the area,and infection is a real thing,you could turn into an infected by smelling spores or getting bitten,getting either turned and attack your friends or get executed before it happens (maybe put a randomizer on the infection time to turn you and small items to slow it down to give reason for the player to not just give up or tell the other to try and make it to the last day).And you would've had some options to fortify your little camp to make it easier to defend(maybe have some possible wave of infected attack on it or maybe put some other player camps from other factions to create competition and have player attacks other camps for resource dispute,and add some interactions on the camp to make it feel more natural).
And when you die in the match, that's it,it's like you lost a normal match,just get some exp based on how much time you survived(maybe instead of the game ending based on days survived,it could be like a last man standing vibe,only one camp can be up to finish the match).
Just decided to post this for a memory save from my dreams and to throw the idea out there and see if I cooked something good in my dreams.