I've been thinking about this a lot. It'd be nice to bring people in to live in the town and maybe like, set them on missions to gather things or let them work on building on the town? At the very least have them walk around and talk to other towns people to liven it up a bit.
The thing that keeps jumping to mind to me is the robots you could recover and send on little away missions in Megaman X Command Mission and they'd bring back weird supplies you as the player couldn't normally find.