As I've already said multiple times, no, we can't. We tried to ban Meta Knight, a character that is almost unanimously considered to be overcentralizing and who single-handedly invalidates the vast majority of the cast, twice. Both times it failed. How, then, are we going to convince the entire community to manually stop people from using two or three specific moves?
This is the issue with this argument, and most Smashboards arguments in general; you guys refuse to look at anything from a sociological perspective. From a purely logical perspective, it's easy to come to the conclusion that if we can make a rule against X, we can also make a rule against Y. But if you look at it from the perspective of "people aren't perfectly logical" it's pretty plain to see why people would be a lot less tolerant of something if you give them the option to automatically turn it off, but would be a lot more inclined to just deal with it if they had to manually put multiple rules in place and make numerous special exceptions.
Competitively speaking, we CAN ban things like that. We shouldn't, and obviously the outcry would be outrageous, but we CAN. We CAN make a ruleset saying "Every character has one allowed loadout. For <Characters>, this is 1111. For <Characters> this is 2122. For Sheik, this is 3111. This is done to give <Characters> a valid chance against the rest of the cast, and to bring Sheik under control without resorting to a character ban." Our rulesets already include several non-game-set rules.
I don't think we should be making special exceptions. Nor do I think the number of rules you're implying is intrusive.
Custom Moves ON.
Equipment NOT ALLOWED.
[Tournament-dependent part starts here]
Players must use one of the pre-defined Custom Moveset Project movesets.
[or]
Setups will contain 8/10 of the Custom Moveset Project. Players may upload their own movesets before their match begins.
Three rules. Nothing hard to remember. No exceptions, all special moves are allowed (unless you run the strict EVO set without imports). The game plays as usual, but with all characters having access to their individual best, or player-preferred, loadouts.
I feel like I should restate here. I don't think any special is ban-worthy, when they are all held to the same standard. And I also don't think laziness, appeals to authority, appeals to status quo, or subjective hatred of certain moves, strategies, or characters, has any place in a ruleset discussion. Without players willing to test the rule, and find reasons these customs should be collectively banned, we have nothing but theory and an entertainingly nice slate of "Nothing terrible happened except people got salty over stalling" with customs. That, to me, indicates that our community is banning them because they don't want to learn. And that disgusts me, personally.
That said, I'm interested to hear your views on Miis, who cannot be toggled off, and cannot be restricted to any sort of "default" loadout.