People make a massive deal about crossover fights but they happen far more than you think. A list I did 7 years ago of crossover fighters.
https://forums.sherdog.com/threads/mma-kickboxing-and-boxing-crossover-fighters.2532995/
Honestly kickboxing, Muay Thai or K1 style rules is the way to go. UFC might not allow but just about any other MMA organisation would.
All boxing fans will dismiss a grappling win and as a fan of both I would take no satisfaction in seeing someone outgrapple a boxer. I would far rather a stand up fight, wether by the rules or at least an agreement between fighters to stand.
Couture had to play the Toney fight like he did because he wasn’t a striker. Whyte needs a striker with the balls to stand with him to make it worth while for the fans.