Hello,
I have few options needed/features for my projects:
1. Limits/end-stops. On each axe, two microswitches NC/NO working as limiters. For example: on roll - limits set at +/- 15 degrees. When one switch is pressed (limit reached) controllers no longer try to adjust position, but only hold camera until angle will be lower than limit. This also can be done with two-IMU configuration without hardware, only by measuring difference between IMU's.
2. "Locking" gimbal - at center or current position - by button or software command "lock" position without stabilisation - for start/landing.
Those options are from my application - gimbal for ortophoto for medium size camera (PhaseOne iXA) for regular aircraft.
(Btw. How attach photos/video to post here?)

Best,

Marek