The base of MMA is jiujitsu, wrestling, and some variant of submission wrestling. Yeah.
Berto would get destroyed by any top fighter. He would probably get stopped by Guillard level journeymen as well. MMA is way different than boxing. The gloves create wreckless abandon offense. Why sit and box when 1 or 2 clean shots will put you to sleep?
Berto with a few years will be Sam Stout at best. Even then, he could get a few kayo losses. He doesn't exactly have the best chin. Nor has great head movement. Forget boxing-blocking with 4oz gloves on.