it might be nice to rewire the trim pot so it sits outside the case
here's an idea, do the modification first, but then wire the wiper pin of the trim pot to your microcontroller
if my theory is correct, you can control the movement and direction of the servo by using one pin
set the pin to low for one direction, set the pin to high for opposite direction, and float the pin to stop the servo, you can probably even PWM that single pin to control speed!
if you want it to be backward compatible with other systems, you can still use it with a Rx, or if you don't need that function, you can cut the signal wire inside and wire that to the wiper
This can eliminate the need for a hardware timer, or eliminate the need for the use of 2 byte integers to specify microsecond delays,