For a rough idea of what you might or might not be able to reach/operate: Sit in the car with full gear or heavy clothing to simulate fire suit, some strings attached between wrists and belt buckle limiting hands to inside of cage to simulate arm restraints, and then check reaches and ranges of motion. When all necessary functions are considered it can get complicated and some compromises will most likely have to be made.
Now is also the time to build in adjustments to fit different sized drivers. That need will come, far easier to allow for now than make the changes later.
Ed