This seems like it requires point-to-point communication; and with accurate MIMO configuration my intuition for the endpoints is that it's like they are communicating with laser-like narrow beams but in RF. But AFAIK multihop communication is still stuck at sqrt(n) scaling, i.e. not viable.

This is all pretty theoretical though, for a small number of nodes like up to 100 it should work pretty well like in the OP application.