I had a few ideas! And of course I can go into greater detail if you'd be interested. Off the top of my head I had wanted to play with the idea of a post-war canon divergence where the Survey Corps travels across the ocean to either North America or Europe (because where are we even) and finds society in the middle of the industrial revolution or even something past that because for whatever reason the world behind the Walls had been cut off for so long the world righted itself while they were effectively in an isolated environment both ways either on the part of whatever was behind the titans or the Wall Cult. Just playing from straight up canon is fine with me, too.

As for AUs I'm fine for anything that isn't completely devoted to being slice of life but otherwise modern or 'like the canon BUT-.' Recently I had played with the AU based on William Gibson's sci-fi Neuromancer where the Walls were pocketed cities called Sprawls but that veers into 'super cool hacker with fingerless gloves' bs that was pure self indulgence. Honestly, I'm open to pretty much anything and like to plan and discuss most any idea after just brainstorming the possibilities that run concurrent with shared interests.