Hello , first of all , english is not my native langage , so don't blame me if sometimes I'm not easy to read ...
Your project is very impressive , and I have one or two questions :
First one : the shaft of the potentiometers are used to support the spring and the pivot arms . I wonder if it can handle these efforts a long time ... It would be safer to put the spring and the pivot arm on a shaft , and at one end of this shaft , a gear . This gear would drive another gear on the potentiometer shaft . I think you have enough place on the base to do this.
Second one : with a larger handle , you should put more buttons , rockers and even a micro-joystick , or a coolie hat : if I understand the way the delta throttle works , you must have the hand always on it , so it would be interesting to have more functions under the fingers ...