As a boxer myself transitioning into MMA your leg gets kicked off and its there for an easy single leg. But its possible to work around it and still keep the footwork there to generate power, i think the people who could do it are the rangy guys.
Wildcard pick for me would be Wladimir Klitschko the way he uses that big jab to keep people at bay, he leaves it out there likes Jones and takes a little step back when ever people throw shots at him. Just that little half step and he is away, not needing the great reactions because the distance he is able to keep. Might work for defending takedowns and kicks...with some training. I hope a prime world class boxer makesthe switch at some point and really gives it a go. All we have now is Hypothetical bullshit and James Toney, a horrible representation of what a boxer might do in MMA.