Gonna be honest, if we really did get a second Punch-Out!! rep, I honestly think it should be Doc Louis.
The problem I have with making someone like King Hippo playable is that he's really not that important than the other boxers, who also aren't any important than each other. Doc Louis on the other hand is basically to Little Mac as Palutena is to Pit, if you know what I mean.
I still am dissapointed that the punch out stage doesn't have special "smash taunt" dialogue with Doc Louise describing each opponent to Mac.