As of now, On normal FW and current CFWs, the gamepad is required to open any system apps, as well as most games. It is also required for the current CFW setups. During my work repairing a gamepad, I found it will not boot without the following plugged in: Wi-Fi card, Display, Touchscreen input, Display backlight. Controls, speakers, NFC, and the dock connector on the bottom are not required for the gamepad to boot. There are many test points on the gamepad motherboard. I have yet to look at the Grandmotherboard (wii u console mobo) but i'll let y'all know if i see anything of interest when i tear down the console.