It's legal, I have friends who used this loophole and have had no issues. I'd be leary of buying a GA car with no title but a bill of sale, even though that's how it works. It would be a hassle to register in MN.
Naah. Again: many states DO NOT TITLE old cars. I have no title for my Duster and couldn't get one if I wanted to-the state will not issue it. IfI moved to Florida, I doubt I'd have any issue tagging it.
So, possibly, "technically" you Could roll "somewhere" get a bill of sale, and registration, THEN a tag from That Place, and just drive it in Your Home State?