Sorry, you're right on the outdoor units, I got my numbers switched. The one I have is a 7762. Not a 7762S, a regular 7762.
It seems to me that if you disable the 5G radio to make antenna changes, you are right in that the mesh AP would be stranded, but that would only be temporary - when you enable the 5G radio, the mesh AP would be connected again.
But my question is still, how to disable the production WLANs, and how to disable the mesh WLAN.
Primoz is right. When you disable 5G radio on MESH AP. It goes offline and disconnected from ZD and Root or upstream mesh AP if any. Post disabling 5G radio on MESH if you have to enable 5G back there is NO way to enable 5G on disconnected MESH AP as Mesh is OFF and this AP is nolonger in control of ZD hence it is stranded. On dual band AP's mesh won't happen on 2.4g on a side note.
On your question - how to disable the production WLANs, and how to disable the mesh WLAN.