1. Player Guilds/Factions or overall a community Hub area.
Having a guild/faction specific safe areas, like a hub for chatting, trading and overall a small safe spot for players, would be incredibly great. Putting up stalls for trading your scavenged goods, LF spots for events/raids/area exploration etc. and overall chatting with your fellow survivors would be a great place for everyone to relax and find their bearings.
2. Griefers/Raiders new gameplay aspect variation.
Well there will be players who will just want to Set the World on Fire so, let's let them but having a Karma system in place, players who misbehave get marked for death by Lawbringers, players with good karma can get special jobs or overall kill such players for extra rewards or cosmetics/trinkets, or the other way around who are too good would also be marked for death by Contract Killers, players with bad karma can get special jobs or overall kill such players for similar themed rewards.
3. Various Events and More end-game content.
Sure nuking places to gather rare materials and fighting powerful monsters is fun and all but having more things to do in the end-game apart from nuking and going in those places wouldn't be enough. What about specific exploration/scavenging/extermination/player driven events that would be quite neet.
4. Player driven content (dynamic game systems)
I think it would be great to see something like players being able to create their own quests for other players to part-take in, like gathering specific items, killing creatures, crafting, defending specific areas etc. There would be limitless things what could players think off, maybe even put bounties on other players, building radio towers to communicate with others, play music.
5. Player Radio stations.
Imagine building, managing and boradcasting your own Radio Station and everything would be happening live. This would greatly co-exist with the 4th and 1st suggestions. Being able to guide your teammates/faction through various areas, having a designated person who watches incomming players or overall controlling the pace of his group or faction in a area, like a commander or a quest giver.
6. Player driven economy.
This will be a survival game, so why not let other players make/scavenge/loot and sell stuff on their own terms. Making many possible player builds viable in various ways. Who knows, maybe even having their own caravans to sell on the go or having it as a portable container.
7. Bounty/Quest/Contract boards.
I would really like to see this made in a safehouse hub. Players putting up requests, bounties or even if possible their own quests for other players there. Looking for materials fast? Putting up a request up there. Want someone dead because he spawn-ganked you? Put a bounty on his head with specific requirements or death counts. And so on.
Sure all of this might not come into the game but it kind of would be cool to me. Sure not everyone might agree with these suggestions but comment what ya'll think about these and what your suggestions or a wish-list might be.