I think a way to make the dunk contest appealing again to bigger names or at least legit rotation players/starters in the league is to partner with a shoe company like Nike, Adidas, Puma, etc and offer a signature shoe for the winner. There's probably a market for a Mac McClung shoe now, especially after 3 peating. If a semi-known player like a Jonathan Kuminga (just an example) won it, he could be catapulted to new heights and I'm sure people would buy his shoe.
That also gives a shoe company not named Nike to carve out part of the market and sell some shoes. Nike doesn't need a gimmick and a signature Nike shoe is something that doesn't come quick or easy. Booker is in his 10th season and just got one, for example. Although Nike might take a chance also.