If you believe in someone enough to give them money for something to which you cannot get title to go right ahead. A bill of sale means nothing to traffic without a permit.

"What do you do with the permit if the buyer has one" Nothing, you want a new vehicle you apply for a new permit, thems the rules. Permits are only good for 90 days in which time you must purchase a vehicle or ask for a one time extension. After that you have to re-apply. A permit only allows you to buy/import a vehicle, it has nothing to do with owning one.