i'm thinking that even if you get your bike registed in MI since you know the ropes, that would be much better than riding with no plate. out-of-state plates w/ current tags tell cops "yeah, i live here, but i'm kinda trying to play right". having no plate is like telling cops "fuck you, i don't have to play right."
pretty much anywhere you go, unless you can claim residency in a state that requires no paperwork fo a moped (which is still a slippery-slope), you could get your bike impounded and never see it again if you have no documentation for it. (edited)