Fwiw, I'm mid build of a controller for a friend with one hand.

I'm riffing off the Ben Heck design https://www.benheck.com/controllers/ but I'm mounting the entire xbox controller on a $15 joystick and then wiring the analog 3dof sensor from the joystick into the xbox controller. So, with one hand, you have access to one origina thumbstick and tilt the entire controller to actuate the other thumbstick.

I've been eagerly awaiting this device from xbox. While it is great, it's just a breakout box, you still need to setup your inputs.

As a side note, are you aware of the class of devices such as the xim4 or the Venom X which comes with a mouse & nunchuck?

https://www.amazon.com/Tuact-Venom-Controller-Windows-PlaySt... (works with xbox)