@ P_Wood: No I'm mechanical engineer. A flying enthousiast with a crack for smooth working electronics fits better.
Regarding your questions, the gyro controls will stabilize the platform, in the same manner they sabilize RC helicopters. I' don't know wether I'll be able to use the IMU gyro input to do that, but when looking at the price for a single gyro I don't think I would bother to separate the gyro input from the IMU feedback.
@nickle: Since I only want stabilization on two axes, I don't see why gimbal lock should occur. In the IMU it might happen, but the IMU will be corrected by a 10 Hz GPS input. The gimbal itself will work from a constant altitude. Therefor I would say, the problem should be solvable. At any given moment you know two positions in three dimensions. The calculation comes down to telling the gimbal a heading and attitude toward an other waypoint. My Garmin GPS is capable of doing this with ease in two dimensions. Adding a third dimension should not be too big a problem? Or am I cutting corners?
Koen