So this is something I talked about in a video a while ago, but I think having the ability to make bases bigger and expand out would be quite a cool feature. Once you have all the basics covered in game like food, meds and ammo, beyond just wandering around clearing infestations there feels to be a stagnation to the late game. I think if it was possible to say build a facility in one of the large slots that allows for the building of things to expand the base and then have different buildables locked behind the facility level.
For example at level 1 you can build wood walls and basic facilities, level 2 you can build stronger walls and upgrade facilities.
Level 3 you can build the walls from the day break dlc. And things like trade stalls, green houses, ect.
You gate it behind your main base requiring power and water. Before you can build facilities you have to have an enclosed area, building of wall sections causes horde raids where you have to defend the workers making the walls. And when facilities are built and your community gets bigger hordes attack and if they break through, your whole new community you can now cater for have to fall back to the original base and you get a massive drain on food and morale and you have to do wall replacements as quickly as possible to avoid problems. I think it would just add an interesting element. And you could have it so players can place either a small slot or large slot that has to fit and there are requirements for different things you want to build. I.e. 2 power sources. Someone with x skill. I think it would make the end game more interesting for a long term perspective. I'll link the original video down below but I have expanded on it quite a bit here given I've had more time to think about it.