As far as SD is concerned, you can register vehicles there and not ever get a SD driver's license. The problem comes in with your "legal residence" state thinking you're avoiding paying "their" taxes. Why not make SD your legal residence and get their driver's license? I assume you think the difference is that you have a sticks & bricks house in MO. If you "move" to SD, you can still own a second home in MO (the RV is your primary).
All that said, seek the advice of a competent attorney because his/her advice will be worth more than you paid here. :)