Actually, with a registered version of FSUIPC you can calibrate your throttle control (yoke or joystick) to achieve total control over the entire range of power settings, from full reverse to full forward thrust.

The chief "problem" with this apporach is that most throttles do not have an "indent" or "lock" position corresponding to 0% thrust, which makes it far too easy to accidentally apply reverse thrust instead of "flight idle!"

"Reverse thrust" in FS is simply negative thrust values, ranging from 0% to around -20% or so...