Yes, I know that gopro is controlled over mavlink+gimbal - it's easy to see that. I am also very familiar with microcontrollers & Arduino, integrating new payloads is not a problem.
The reason I mentioned LANC was just because for this camera, I also wish to control zoom levels, manual focus and some other settings. So LANC protocol it will be.
Solex's new feature (remote command) will indeed be useful in the future, for now, do things without it.