Marcus Davis and Chris Lytle both have had bro boxing careers. I don't know that there are really any pro mma guys right now that would make the transition to be elite level boxers. Could they make some money, and have some competitive bouts? Sure, no question all of the guys you named could and so could a lot of others. The thing is, and don't get me wrong on this I love MMA and I will take good MMA guy over ANY boxer in an MMA match, however the fact of all sports and combat sports in particular is that the more restrictive the rule set, the more specific the skill set, and the more specific the skill set the longer it takes and more adept you must be to be considered among the best. Think of it this way. If you take one hundred identical guys, fifty become MMA fighters, fifty become boxers. All physical and intangibles(heart, desire etc.) are equal. Yes the MMA fighters will have much more to learn, boxing, kicking, elbows, take downs, takedown defense, control and clinch grappling, submissions and submission defense etc. And that may seem overwhelming, but they can be good at most of it, great at one thing and become a high level MMA fighter. Think Chuck Liddel, great power, good wrestling, control ground game etc. Now look at the boxers. All they have at their disposal is jab, cross, hook, uppercut, over hand, and all of that only to the upper body. Those fifty guys are going to have to work long and hard at that extremely limited skill set and restrictive rule format to reach a point where they are considered great. The difference between a great boxer and an average boxer in minuscule, while the with an MMA fighter if a guy isn't so good at take downs, or submissions he can cover that up by being solid at all other phases. So, I am not really sure that even some of the best MMA boxers would be good pro boxers in the sense of being title contenders. But, by the same token, Boxers for the most part have trained and refined boxing to the exclusion of every other facet of the fight game. In an MMA fight an elite level boxer is essentially a one trick pony. Sure, that is one hell of a trick, but if you avoid the KO, the fight should be yours.