Custom linux drivers could be written for the Wii U gamepad, giving Trinux (in U mode) the ability to utilize it.
That being said, writing drivers is above my skill level, but i know that Ninja_Carver wrote a lot of the drivers for the vWii himself. I cant speak for him though on whether or not hes up to the challenge of writing gamepad drivers for U mode.
On a side note, i want to see a plethora of alternative OS's flourish on the Wii U, the more the merrier! As the scene matures and we reach the point of having multiple alternative OS's on the Wii U, I'll be one of those nut jobs with all of them on my Wii U including the official CafeOS XD
gonna have to correct you here. I didn't 'write' any drivers for vWii, though I did manage to hack some together on some occasions. I don't possess the skills to write new drivers, but I sometimes get lucky and can get shit working . I don't think I'm up to this particular task though...