This question is more for mods that aren't being worked on by mod authors/teams. There are already so many excellent mods out and many great mods in the pipeline that improve just about every facet of the game.

For me, after playing JK's Stendarr Rising mod, it made me wish there were similar mods for the other minor factions in the game that worked that well (with perhaps more end/recurring rewards). You can even do it for the regular, joinable factions/guilds too (creating an Imperial base, build it up, and defend the base against waves of stormcloaks, etc).

But I love faction overhaul/improvements in general. Really good mods that make you a part of a faction (Silver Hand, Forsworn, etc), have a home base that you can improve, recruit and assign followers to join the guild, maybe throw in a quest or two, add a radiant quest system to it plus "defending your base against waves of attacks", and I'm sold. It really adds to the roleplaying aspect of the game too. You don't even need original voice acting and you can just use vanilla assets to make it good (as Stendarr Rising can attest too).

What about y'all?