Looking for advice. Short description is let's say we have a military tank (I don't). Two tracks and there is a single lever that controls forward and reverse to each single track. Easy enough to add a servo or stepper to each lever and a single axis joystick with a control board to have linkage less control to the control seat. Here is where it gets complicated, that requires two hands to drive, if a hand is needed for any other purpose you would need to come to a stop to perform said task. My question is this, if I have one single axis joystick and a dual axis joystick and a multi contact toggle switch (or similar device) sends total control to the dual axis joystick, how in the heck can I "blend/mix" the signals to control the steering of the machine as one servo or the other or both need to be manipulated to accurately turn? Arduino or other computer based options are at the very bottom of my list as keeping spares on hand would be difficult in the event of failure out in the boonies. If I can built it on the bench here I'll do a full write up with pictures. Thank you.