Would it be possible to set up a BLE mesh so that IPhones and Macs could pair to the mesh, initiate AirDrop, and use the access points as wifi repeaters (or just run the data through the existing network), allowing airdrop to happen at longer ranges than the native antennas of the devices would allow?
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.