One thing that I have thought about quite a lot is what would a town building/control system look like in ESO. Full disclosure, I started thinking about this a lot when I began to worldbuild a story based off of a 4th era descendent of my current in-game oc. It surrounded the potential story of Mathiisen Manor and turned into me thinking about what it would be like for us to be able to "liberate" or take control of a town via the storyline and then be able to guide its development or at least its appearance in a way that is similar to how we can currently interact with our own homes.
For a house like mathiisen manor, it would make perfect sense if we got that home after becoming the new canonreeve of Mathiisen and the town became ours to lead and protect. Want to turn it into an Embassy town? Grow a graht-oak in its heart and appoint a treethane to lead in your absence. Want to emphasize the forge? Expand the port aspect, train smiths, and welcome new ships to the city. Build new city walls, set patrols, engage daedric assaults, repel vampire attacks, and push back coastal raids by Sea Elf pirates.
Imagine a future DLC with a system to hire and train your own city guard, to have the town grow and follow your ideals. Set patron deities, open a temple, welcome displaced refugees from the Three Banners War or use the town as a training ground for your alliance's elite forces. Want it aligned with the Mages Guild or the Fighters Guild? Have them make up the bulk of the npcs that appear, alter the guards' uniforms and armor, select what banners appear, etc. The possibilities are endless and there are already several houses in game that could serve as a basis for this kind of story/world building based expansion. Mathiisen is only the one that I've thought of the most.
What about you? Is there a house in game that YOU would want to be your base of operations? Would you want to become the latest Thane of Skyrim, Canonreeve or Treethane of the Dominion, Lord of High Rock? What ideas do you have for a potential future system like this that would serve as a massive expansion of the housing system?