*facepalm* How about actually getting accustomed to the 3DS's control scheme rather than waste time and effort making gamecube controllers an option that's not even needed for a system like handhelds! Trust me, smash bros on a handheld works better than you would think so long as you know what you are doing!
I agree with you to a degree. I have nothing against the Game Cube controller, but honestly people should at least try to use a different control scheme. As it applies to the 3DS I don't see it as being nearly as competitively viable as the Wii U version, and if you have to want to use a Game Cube controller well then that is why there is the Wii U version. The 3DS version I think will be a mostly casual type thing, and if people want to play it competitively there is such a thing as the 3DS Pro Pad ya know.
However I can still understand why someone might want this, even if its counter intuitive. After all its a handheld for a reason, its not really meant to be played quite the same way as the console version. Everyone knows this but chances are unless you don't own a Wii U you will probably only play this when you have nothing better to do, or you are on a long trip to somewhere. Now I feel like while the person that did this in a way is ingenious one problem is that how would you really be able to play well if the 3DS isn't in your hand? Like some people have mentioned propping it up, but that seems extremely awkward. Not to mention it feels like a massive tease to the people that actually want this since the guy doesn't seem to have plans to sell this, and I'd imagine trying to would present some issues, assuming Nintendo hasn't gotten wind of it, I dunno lol I just think its unnecessary.