I thought about this too. I think it can work, though you'd likely need a strap for the gamepad just in case.
It is pretty much the only way I can see them implementing SS's motion controls (which I thought were great, the swordfighting at least, wouldn't want to go back). That and using the Wiimote/Nunchuck combo with the gamepad as map screen in front of you, but I don't really see the point of that.
Maybe they could use this (in the OP) as a control input, and devise a more traditional control input for those that don't have Motion Plus, or don't want to use motion control. Hear me out;
SS doesn't have a traditional option because there was no way you could do the combat or the puzzles with button controls. the WiiU gamepad has a second analog. What if they could make the right analog also control the sword? Move the stick right > Link swings right. Move it up > Link trusts upwards, and so on.
I think they could make these two inputs work.