I actually have quite a few qualms with the "common presets" plan. Keep in mind that I desparately want customs legal on the map in all forms.
1. There is a strong chance that high tier players will have more than just a single set of customs mastered, because it's almost inevitable that we will deal with the issue of custom move counter-picking between matches. Some moves will work better in some match-ups, I think we can all see that this is bound to be true. Singling out "common" presets essentially puts us right at square one, with everybody using a single, predefined custom loadout, essentially taking away the actual depth of custom moves. Now you're just preparing to fight a character with consistent x custom moves rather than that character with an adaptive moveset catered to that players playstyle, which is in essence the whole point of custom moves to begin with. This is now a display of what we call the illusion of choice. If any one single choice is clear and cut a better choice than the other (or rather, the only choice available in this case) then it's not really a choice, is it?
2. That being said, this would be worthless to mention if I didn't have some kind of alternative plan to address my concern. I simply feel the preparation should be put in to transferring all the customs of the characters beforehand. I see a lot of talk about tournament preparation hell and organization hell, but people need to start buckling up if they want Smash on the map professionally for as long as is possible. Tournaments needs strong coordinating skills and proper, prior planning. Each tournament needs care and thought put in to its planning, and that includes ironing out systems with all custom moves available.
There's pretty much no point in allowing customs if everyone is forced into using the same custom set, I hope you can see that. If the option to modify the character in a unique method is not available, then the purpose is then defeated.
I understand that many customs can be seen as ineffective, as well, but who's to say it lacks a purpose in some matchup, somewhere in the game. We just can't predict that. That's why we should make the effort to ensure that the full range of options is available.