I have been playing fallout for awhile now, and my girlfriend and I have had an amazing experience with the settlement system. The whole decorating and personalization aspect of the game really bring the game to life and I think that is what makes it such a great game to play. I have a few ideas that I would want to see in a possible future dlc, or patch.
First of all, I would like a system that could allow us to visit someone else's settlement and/or potentially work together to fight off a huge invasion or something. To do so, I think each person would designate one of their settlements as their home base and friends or other players can come and visit or maybe even invade your settlement( much like how in dark souls other players can join your game). Furthermore, I would also like to add a system in which you can leave weapons that you want to share in containers so your friends can have access to weapons where they otherwise wouldn't have. This can work both ways, and I think it would give the game more of a dynamic feel to it and really bring it to life.
Secondly, i would like to see a more interactions between our settlements and our actual combat experience. For instance, we can send a group of settlers to go hunt and they could bring back rare food/plants/weapons that we otherwise wouldn't have access to. This I feel will make the settlement system seem more rewarding and add another layer to obtain rare weapons.
Lastly, just overall more figure and customization options. But, I am sure that will come with later dlcs. I am just hoping for more personalized set peices and more options to make your settlements do more in supplying/supporting you in combat, so you can be more of a strategic commander rather than simply being the best fighter.
Thanks for reading and I apologize if these suggestions have already been mentioned.