Mature little angry man aren't we?
The maps arent suited for it. a 20 foot ape is a 20 foot ape.
The game play isn't suited for it (how would you reasonably attack that thing? Hrm? Adv.melee would be boned)
Ways it could work :
Lose the very roots of your idea. Keep only the basic concept that it's 1 v all and that one is quite powerful.
Replace that Ape with something of a Broli ish nature (not suggesting him, since it's a movie char, but bare with me) where it is quite powerful, just not as massive and game dynamic changing. You get all the destructive power, but in a package that makes sure you can still function in proper form.
Basically just some thing with a high PL but low map nuking ability. Think Trunks before ssj and with alot more power. Good at melee, has a few interesting beams that are tools more than wepons and is relatively fast (eh, when transed)
The problem with said mode of game play (outside of the actual sizes and what not) is the fact that you cannot effectively use numbers as much in this mode version. Before, with melee, you simply sent them flying to be dealt with by who ever got there 1st. Factor in advanced melee and you have mainly a 1v1 competition with something you can't take head on.