Sorry, I'm just imagining you in a heated battle and the wheelchair losing connection and immediately reverting back to controlling itself and thus flinging you around. ;-)

Have you looked at Steam Input? You can do a ton of stuff with it, maybe even combine multiple controllers. You can even use it with none-Steam games by adding the executable to Steam. It only has problems with flatpaks.

Or maybe look people working on Joycon support. I think they are technically two controllers that you would sometimes like to act as one.

Hmm I wonder if antimicrox would allow you to combine two inputs into one composite input, I don’t have experience with it so I can’t say for sure but it seems like the kind of utility that would.

https://github.com/AntiMicroX/antimicrox

What I would do in this situation is map the controls to keyboard, then use a Controller-to-Keyboard mapping program to map all the controller buttons to the keyboard buttons. So map both controllers D-Pads to W-A-S-D (or arrows, or whatever really) then set those keyboard controls to your movement controls in the emulator.

https://www.reddit.com/r/EmulationOnPC/comments/165tewk/mapping_multiple_controllers_to_the_same_input/

It seems like it should be trivial to create a controller device that maps the input from two other controller devices

i only know in some games you can customise controls like "walk up=joystick 1 x-axis minus", "turn right=joystick 2 x-axis minus" etc. that allows to configure multiple inputs. i use this for Spiral Knights playing on Linux with controller and trackball.