Well, you are right about "pretty flat around" Detroit/Ann Arbor. It is a pretty tall order to be looking for class III+ to class V! Was that somehow a surprise to you? I mean, really, your high school geography classes didn't tell you the Upper Midwest is not known for it's mountains and mountain streams?

(Sorry . . . don't really mean to be rude or snide . . . just pointing out what should have been obvious.)
However, things are not really that completely bleak. Yes, you will be doing some driving to find III+ to V, and you will not find it too many months of the year, or too many days of each month. But you can find it if you know where. Don't look for it in lower Michigan . . . nothing there will approach III+ to V.
As you hint, you can look north (to Upper Peninsula Michigan) and you'll find a great assortment to pick from, but you will be looking at drives ranging from 8 to 12 hour (or more) each way. Looking west, there are random bits available here and there (Indiana has a couple, Wisconsin a few more, and so on) or there's really looking west (to Colorado, etc).
However, your closest options are about 3.25 hours to the east, in Ohio. If you check out (click the link):
Ohio - Southern Lake Erie
you'll find a small assortment of options in the III+ to V range (Tinker's Creek, parts of the Cuyahoga, etc). Or to the south (again, still in Ohio), you're looking at about 5 hours to runs listed here (click the link):
Ohio - Middle Ohio River Drainage
Rob Smage
AW member since 1992, volunteer since 2000, Midwest Regional StreamTeam Leader