I have modified my throttle handles.

Instead of using microswitches for the reverser I have installed a small 10K potentiometer.

This allows for me to move the handle a quarter up hand hols it there to apply 25 % of the reverse thrust and so forth.

See how I have done in this video.

You can get the potentiometers from eBay. I bought mine from TaydaElectronics.