What about Wand? He would be a good choice. You saw his dismantling of Kazuski Sakuraba.
I'm surprised at the number of people who mentioned Wandy. I love theg uy and he's really entertaining but I can't see him lasting in K-1. Look at the most successful champs, all very disciplined fighters, crisp striking and excellent defense. I think Wandy's success remains with MMA.
Rampage has fought in K-1 and been successful, I'd be interested in seeing him fight Remy. If Machida would push the pace relentlessly, I could see him being a force for Heavyweight...