Proof of Concept: The Mavic with the GoPro Hero 3+ Black, mounted on top, was both very successful at capturing the full 360x180 scene, and ~ it will be the last time that I will be using this setup...
I set the Mavic to shoot 5 Rows + 8 Columns + 2 Nadirs, including the 30° up-angle from the horizon ~ all shot in landscape mode. The GoPro was mounted on top and tilted at approximately a 45° angle, in portrait orientation, with a 122° field of view (FOV) from horizon to zenith. Autopano Giga did an excellent job of mixing the landscape images from the Mavic with the portrait images from the GoPro. I ran the stitching once and there are no apparent errors in the panorama. It rendered a perfect 360x180 spherical image (see link below).
However, the weight of the GoPro rig had the Mavic rising and falling, every time it rotated to shoot the next column of images (see video below - low quality video as I was digitally zoomed in on my cell phone). You can also hear that the pitch of the motors is much higher than usual - meaning, they were working overtime. When I got her back on the ground, all four motors were very hot, especially those in front.
I think I'll be looking at getting one of those cube-shaped sports cams with a 220° FOV, and just mounting it on top, aimed straight up.
So anyway, that's how you can shoot the sky when using the Mavic for a 360 pano.
Perfect 360° x 180° panorama shot with a Mavic Pro w/GoPro mounted on top:
The rise and fall of the Mavic while carrying the GoPro Rig: