I've actually tossed around an idea before, keeping most of his Brawl moveset and throwing in some new attacks, a Bowser revamp basically.
For the most part, he'd keep his tilts, but whip out his sword for smash attacks and his Nair, Bair, and Fair. His Uair and Dair would stay the same, his regular A hit would basically be the same, but could be held down for a mini Warlock Punch. His dash attack would be the same at first glance, but quickly smashing the button again will cause him to swing his sword out after the initial shoulder charge. And then his neutral special would be the coveted Dead Man's Volley, which needs no explanation. His side B would stay the same, but perhaps give him more distance in the air, or keep it's normal distance without leaving him helpless, his down B would also stay the same, with possibly more utility. His recovery would be similar for the most part, but would have more range and control, something like a really gimped version of ROB's recovery, he would do the initial lunge of the original recovery and then be able to hover slightly for a very short time. Other than that, he could really use a bit more speed and jumping power, I know Sakurai was going for the big brutish thing, but he's surprisingly nimble, that jump in TP.