I have been playing this game since Alpha2, it is my and my son's favorite game to play together (he's 14). We have written a few suggestions that would increase longevity of gameplay, efficiency and fun.
1. Decrease the stupid wasp noise, way too loud and obnoxious
2. Incorporate rope, and simple machines including but not limited: pulleys for drawbridge function, trip wire, netting, and levers.
3. Equipable ruck sack for additional storage, but decreased speed.
4. Weather? rain would dampen smell and sound sensed by zombies, slow player... etcetera.
5. A zoomable minimap
6. Ladder lock, jump to eject, I have died way too many times falling off of a ladder.
7. Easier book reading for recipes.
8. Laser sight, red dot sight, and mechanical sight. Add a sword and a spear.
9. Alliances, groups, clans?
10. Big military base instead of those small camps. a lot of loot a lot of risk.
11. First aid kit to restore either half or full health.
12. Restaurant food prep/ovens and MREs
13. Fall breaking: IE pressing space bar breaks fall.
14. Silencers for the weapons
15. ammo in inventory carries to belt with a reloading speed penalty instead of having to manually transfer
16. Stamina regens faster when undected, slower when detected or hunted.