idk how much of this is going to come up in the fic ever but there's two parts to a kleos (kinetic-link exonervous operating system), one that has basically the entire control scheme of the machina and one that is synced to the pilot's resonant (or echo). you can make multiple of the pilot-side interface for the same machina but the machine-side and pilot-side have to be carefully linked together. and then it basically puts you in echo-vision rp duty mode but instead of perceiving yourself as someone else's memory-body you perceive yourself as a giant robot in real-time and your hands move on the controls instinctively, like how you don't have to think about what muscles to move to walk.
this means that kleos-equipped machina can be piloted normally by anyone (who knows how to. pilot a giant robot) but you need a separate pilot-side interface for each echo/resonant-having pilot in order for them to use the system.
also the pilot-side interfaces look like cute hairpins
(KLEOS backronym credit to @yrgirlkv)