The problem with this is Nintendo wouldn't have any control over software licensing fees. For example if say Capcom wanted to make a game using this controller, I don't think Nintendo could make any way that they collect a licensing fee like they would on a platform they own. Apple/Google own these OS' so that would be out.
If NX fails though I could see Nintendo doing this and just throwing their entire weight behind mobile. In 3-4 years by the time something like that would become clear, the standard smartphone/tablet processor will be pretty beefy too.