In TN, swapping VIN plates can be done legally, as long as the proper paperwork, etc., it done. It's used mostly when doing a body swap/major repair to a car. Hell, the VIN on my Jeep is mounted to the fold-down, easily removed/damaged winshield frame! So if I ever get around to replacing that with a new one, I will have to swap over the VIN plate.
As far as using the process to register a vehicle that is normally not legal in the US, the system probably has enough loopholes to be able to do it without much trouble.
Personally, I would think it may be easier to use the system that custom car/hot rod builders use, which provides a way to register, etc., a vehicle that did not come off a production line. Don't know if it would work on an imported vehicle though.