If you are worried about someone taking it off the wall then you are addressing a difficult security issue, because you don't have physical security.
You could consider getting a toughened plastic ABS box (such as an electrical cabinet) and putting everything inside of that. Put a "Danger Live wires" sticker on the outside.
ABS plastic electrical boxes are easy to get hold of and relatively cheap.
The "Sticky mac" idea - you'll need to be careful using that approach. You would be restricted to using NAT mode. If you use bridge mode than the switch sees the MAC address of all the wireless clients - and they would get blocked.
There is a feature coming up (don't know when or what models will support it) where you'll be able to say this switch port can only have a Meraki AP (or MX) plugged into it. The switch authenticates the Meraki device using a cryptographic method.