KneeOfJustice99
Smash Champion
I think customisation would be cool... but I'd personally just keep it to some kind of system where you can make your own alt colours for characters (and their alternate models.) That way, you're in a happy medium where you can still create cool stuff or things that are references to other things - but you don't have such a degree of customisation that it needs an active moderation team constantly trying to determine if players are making Mario shout slurs whenever he does a forward smash.