"The majority of the community is in favour of customs."
Of casual gamers, yes, but every competitive players are against customs. Or at least, 95% of them.
"Picking random character has to be banned at custom tourneys, right?"
Nope, cause it's not random at all while the match played.
Customs are a little bit randoms cause it adds randomness to the first match, as they improve how a MU is favorable to a character or on another.
In My Opinion, the ideal rules would be like that:
-A list of banned custom moves (Some on top tiers like Diddy, Ness or even some on Link are completely broken, I can't make a perfect list by myself as it would ask something like 100 hours of testings and my list wouldn't even be widely accepted.
-A number of custom moves allowed depending on the character. For example: Palutena can have 4 custom moves, Diddy can have only one.
Allowing all the custom moves is a ******** thing to do, I honestly think it's just a way Melee players have found to kill smash 4 on the competitive scene. Making "fun" rules that aren't competitive just to make the competitive scene die. But hey, it won't happen, in mst countries custom are simply banned, and if you don't stop to say that all the customs are balanced, custom will NEVER happen.