As you know gamepads always center there stick and it's hard to get a stick value that is not MIN, MAX or CENTER. It's to sensitive to have a good throttle control.
Now I'm implementing a gamepad throttle mode for my project (in the arducopter v2.5.3 firmware)
A very simple/basic overview of what is happing in the code:
When flying in THROTTLE MANUAL MODE then
-> throttle value = stick position
When flying in THROTTLE GAMPAD MODE then
-> stick posistion = center? do nothing: leave throttle at it's current position
-> stick posistion = down? decrease: throttle value = throttle value - some value
-> stick posistion = up? increase: throttle value = throttle value + some value
This way it's much more easy to control the throttle with a gamepad and to hold it on a fix position. But it also has some disadvantages. Increasing or decreasing to full max or full min will take some time. But if someone would work this out this gampad mode could be tuned with configurable sensitivity values etc to minimize the disadvantages.
concept video, with really basic/raw code just to show the concept