AirDrop over Access Point BLE/WiFi Mesh
Airdrop already forms a mesh and doesn’t need WiFi networks to broadcast airdrop. 

Existing  Apple hardware 
builds a point to point mesh and you can airdrop across the mesh far larger distance than the range of your device alone. 

So you don’t need to build anything but could have a functioning mesh. 

There are improvements in hardware about to ship so we can revisit this answer when iOS 13 ships and matures and the new hardware ships and embargo expires for people that have seeded devices for review.