This is a bridge to cross when we get to it.
Worst case, the following happens:
- It's hard/annoying to unlock customs on WiiU
- 3DS data cannot be used to permanently unlock WiiU data
- There is no hack/cheat discovered to trivially unlock them (there already is a powersave hack for 3DS)
- Some setups at a tourney do not have everything unlocked
- A player wants to use a set not unlocked on a setup, nor previously transferred from a 3DS
- You take an extra few seconds to transfer a profile from a 3DS
That's a lot of ifs, and it's still a narrow case. The AVERAGE case isn't bad; maybe most of your setups
do have everything unlocked, the setup(s) without everything still have most stuff, and the important, frequently-used competitive sets it doesn't have have been transferred previously. (Including in advance at that very tourney.)
Fundamentals are still king. For all the good things custom moves do, specials are only a fraction of the game.
To some extent, I think the inherent lag of online play is about as much of a game-changer.
First, I guarantee you that replay data can be sniffed to list equipment. Like, the data simply has to be there for replays to function. We just haven't cracked those files yet. (No need, previously.)
Second, meaningful stat changes are pretty easy to notice--for both offense, defense, and speed. You have to be really conservative (<10% for sure) to changes in anything to fly under the radar. Additionally, all of the special effects except easier powershield and sort of smooth-lander are really obvious.
Edit: The combined implication is that sneaking equipment into an online tourney is a very poor risk-reward. You get extremely little payoff, and it only takes one suspicious, paranoid, or just outright diligent opponent to ruin your online tourney career forever.