cool project. Can’t wait to see the video
I assume you’re referring to the ISOx16 module https://www.ghielectronics.com/catalog/product/391 ? it uses a Y socket, so is using standard IO pins, in a pseudo-SPI form. You can possibly get away with using a custom wiring using shielded cables, but you’re pretty much on your own if you do so. Given it’s only you in the exoskeleton, you’re probably going to be taking all the risks yourself anyhow right ?
If you look at the ISOx16 module schematic, you can see it only uses HC595 logic chips, so they will be somewhat more prone to spurious bits affecting the port outputs, so I would suggest trying the other side first, run long cables for the joystick and display. The display may also be affected by the signal length, but at least that doesn’t turn motors on or off at inappropriate times
If this becomes more than tinkering in the back yard, you might want to think about industrial standards, like RS-485, that protect signal integrity, but that’s likely to imply you will start adding separate processors for these separate functions.