He's a flawed by exciting fighter. There are plenty of them in the UFC and there's no reason why that should preclude Melvin from joining the organization. He's no more flawed than, say, Palhares - in a very different manner - yet Rousimar is a UFC vet who has fought several top 10 MW opponents (Marquardt, Hendo, Belcher, Lombard).
Even at this stage in his career, Melvin would still knock the block off of most MWs who didn't tippy toe around his lethal kickboxing until they could take him down and work on a sub.
I'd love to see him in the UFC. He'd be a solid draw.