Some of these would be great! I've already seen a pic of a new MF, so that's on the way. It looks just like the last one. I agree, a UCS AT-AT would be amazing, but I'm a sucker for the classic walkers. Here are some other ides:

Hoth Patrol: Have Luke, Han, 2 Taun Tauns, some Hoth scenary, and an actually accurate Probe Droid

UCS Echo Base Launch Pad: Interior of the base with maybe 1 vehicle and room to add other official sets like the MF and X-Wing

a new UCS X-Wing (cause I didn't get the first version)

I like the Cloud City idea, but what if TLG did a series of little sets that go together like they did with Jabba's palace: Dining room scene, Han's torture scene, Leia, Chewie, R2, Lando escaping from the Stormies scene, docking bay scene, etc

I like the Dagobah training set idea too. Maybe have playable features like floating rocks, R2 and even an X-Wing?

Maybe some little scenes on the Tntive IV: Stormies/Vader entering, Leia recording her message, etc.

I've got a TON more, but am tired of typing...

a new UCS X-Wing (cause I didn't get the first version)

This isn't a legitimate reason. If everyone proposed sets they simply missed out on (for whatever reason), we'll be bombarded with clone sets for a minority of collectors.