Mount your throttle and joystick on a chair with a folding leg rest. You dont need a new chair, just this bracket.

[AngleOff66]

https://www.amazon.ca/Ergonomic-Keyboard-Compatible-Laptop-Workstation/dp/B0DWJ3HGJL?

Edit: 

Had a thought and to make the plate and joystick removable, he could just use some of these quick release levers where he uses screws on plate to atach it to the tube metal.  

https://www.amazon.ca/Bicycle-Release-Skewer-Cycling-M8X55mm/dp/B0D9GDGVBQ?th=1

If thse after market brackets can fit on your current chair, then  you dont need a new chair.  My idea is to cut them so they are a bit narrrower and have them welded.

https://www.amazon.ca/JECOMPRIS-Ergonomic-Retractable-Office-Chair/dp/B0FCCL6WKH?

Sure you have to remove the joystick when done, but beats buying a new chair.

 

Edited September 2 by AngleOff66

[SharpeXB]

Nice solution. Figuring this stuff out is just nuts sometimes!