I didn't say he was capable of doing it. I said mavlink is not required. But none the less, you solder one wire onto the main board servo 6 terminal at the accessory bay, and set one parameter to enable gimbal pitch on servo 6. That's remarkably easier than a mavlink gimbal, which as of right now, requires non-existent software and firmware changes to work properly. Soldering one wire is a lot easier than debugging firmware...
Down the road, a mavlink gimbal with a plug and play connector to the Solo's existing connector would be ideal. But for that to be useful, corresponding firmware changes are needed in the old solo ArduCopter, the new ArduCopter 3.5, and the gimbal controllers from storm or alexmos. None of this exists today. PWM exists today