I don't have time to work through these - I have to work at 4:45 in the morning! - but you're right, there are lots of options in central Iowa.
My thoughts earlier were that Waverly-Shell Rock would likely come to Xavier, and I still think that's very likely. The losses by Ballard and Clear Creek-Amana kinda complicated things, though, so some #2 district finishers will get to host now. The question, I guess, is what will the state do with Webster City/Gilbert/Waverly-Shell Rock? They probably won't have WSR play West Delaware (same district), and WD can't play Xavier (both district champs), so you almost have to match WD and Solon. Washington could play Pella, or even Carlisle, maybe. Or the state might match WSR with Gilbert or Webster City and send Washington to Xavier.
Lots and lots of variables, and I don't have time to look them over. It will almost certainly be either WSR or Washington at Xavier, though, and I just have a gut feeling it'll be WSR.