Lots of KR love... I'm inclined to agree with Battle bunny though. It seems that while the civil war would be an exciting, AAR, once it's over with, there really isn't much left to stand in your way with the full might of the USA behind you. At that point, it's pretty much your choice of who to steamroll next. With that in mind, I think I can nudge AUS toward the bottom of the list, if not off it entirely.
I'm curious as to why HoI3 wouldn't be worthwhile -- it seems like it opens a lot of opportunities, even if it might not be as readily moddable. At least as a minor nation, it seems like it could be very enjoyable to get to know the new system while playing around with some of its options. Hungarian infantry marching along license-built German panzers? Sounds tasty...
In the KR arena, even if KR AARs have been done and redone and overdone, it's still tempting just because there's SO much character and narrative in the world. Romania and Austria are still big frontrunners in my mind - either creating a giant Imperial Austria, or going the Danubian Federation route. And playing as tiiiny little Romania and trying to establish an Orthodox powerhouse could be fun, too.
I should look at some of DH's other mods, as well -- perhaps one of the mods, or even the WWI scenario, could provide an interesting setting.. God, I've got AAR ADD...