I tired printing this just for the heck of it. It printed well enough (I printed the concave version), and the support structure beneath broke away with no problem. Only downside was that the four "nibs" inside the concave top was too sharp for comfort. Are they really neccessary?
Attaching it to my Switch JoyCan was not so easy, though.
I trinted it in PLA, and there was not enough flex in the little legs/clamps to grip onto the joystick. And I didn't was to use too much force, fearing I'd ruin the JoyCon. I gave up after a little while, and then noticed that one of the legs had broken during my attempt to attach it.
Printing in flexible PLA should make it attach more easily, but might also make it come off just as easily. Andd there's the problem of flexible materials not playing too well with support structures. That last point could be offset by flattening the top and printing it upside down.
All in all, a nice concept and one I'd like to see succeed, but it need a bit more work.