I've been thinking about something similar in my head but this is amazing.

I was thinking about a possible 'Guild Shelter.' Which I imagine we will be needing in the future.

What is it?

• Its a complex big shelter which can hold multiple people who must've got together to help each other forming a Guild.
• It has separate chambers for different members and a common area for crafts and survival items, such as a furnace shed, BBQ room, roof top dew collector and under-foundation animal traps and possibly some more in the future.

• Maybe a garage (under-foundation space?) for a pick-up trucks used by guild to make scavenging runs to the towns etc

• Its a huge/tiered shelter for multiple people to live/store stuff and have common provisions/utilitites (Furnaces/BBQs/Dew Collecters/Future items) to share.

• These people must have got together as a band (Guild?) to help each other to survive. with a possible tiered/ranked hierarchy of members.

Why we need it?

• If you make shelters just for yourself, they are more vulnerable to raid attacks by both players and zombies hordes (Possible PvE feature?)
• Hard to defend shelters just by yourself when you're outnumbered.
• Resources won't be as easily available as they are now, so if everyone can pool in their scavenging loot they might be able to share some structures and help each other out.
• Survival by yourself is or should/will be hard in the future. If there is a system in place it will be easier as different people can work on different areas. Tools scavenging, food scavenging, hunting, metal etc scavenging, patrolling, structure repairs and so on. Which otherwise might be impossible to do all by yourself.
• If we have roles in the future (medic, mechanic, hunter etc) it will be really helpful to band together to become more effective.

How to organize it?

• There should be a roster interface available to add/remove/manage/view members of the guild.
• There should be a rank hierarchy in place with guild founder at the top, and new recruits at the bottom.
• To avoid 'traitors' or 'infiltrators' lower ranking members won't be able to access high ranking areas in the shelter. This is where tiered structure comes really handy as we can set different pass codes to different areas and disclose them to members on promotion.
• Promotion policies can be figured out by guild. Some may allow only the guild master to promote. Bigger guilds may allow couple ranks down the hierarchy to promote others based on trustworthiness, contribution to the guild and so on.
• Bulletin board to list the necessities/tasks of the guild so people can figure out what needs to be done.

I think this will give players amazing survival experience. This can lead to multiple things like, guild wars, seize attacks by other guilds, defense against such attacks, infiltrating city as a guild (which I imagine should be impossible to do alone in the future, like Atlanta on walking dead? :P) and so on. All in all this will also give a sense of 'progression' to the game.