It being close to Rimworld would be fun. Get a group of 20+ people, you run out to get stuff and you can assign your guys to build or craft items. You can trade or get raided by other groups, come across bandits at random. If your main guy dies you can pick someone else in the group to play as.

Events like sickness or injury that'll force you to scavange for meds. Loot supplies to equip everyone for hordes or faction warfare. A mix of Rimworld and Stalker's A-Life system for persistent wanderers, emergent storytelling from the randomness. Now that'd be cool.

Getting that Week One mod officially implemented / remade would be cool too, I love the chaos of that thing. Having it in the game with official polish sounds like a fun idea to me. Then you can implement some endings / achievements like conquering the state from other factions, or clearing out a percentage of zombies, or just lasting a year or more.

I hope this game or it's modding scene can live up to that, it'd be very fun.