Right now the only issue would be the buttons which would depend on the haptic feedback which we cannot know if it's good or bad until it's revealed/demoed. Other than that the idea is sound based off the patents.
Just needs grips...or maybe it's more comfortable than it looks (Wii U gamepad was massive but didn't feel awful)
Also, the Wii U's issue wasn't the gamepad but the marketing (including advertisement and price)
The gamepad didn't provide a detrimental experience.
There should also be pro controllers for multiplayer since I don't think Nintendo would make people buy four of these to play something like smash or mario kart