Perhaps the solution is to use the mouse for navigation like Quake. I believe this device to be the best control for FPS's. Now to use it for aiming, we could use the second button. Say to release the mouse of control and have the cursor move arround for aiming. Then pressing the same button to enter back into navigation mode.
To make this switching of mode faster we can copy the pedal idea of "Time Crissis." Say while holding button 2 the cursor becomes independant of navigation and releasing it put's it back to the the middle of the screen like in quake. This could actually work.