Blocks are just transaction data which has almost all already been relayed through the network. All that one has to send is just a tiny set of indexes to indicate which of the txn in circulation were included and in what order  and there are already alternative transports that do this (or even less-- just a difference between a deterministic idealized list and the real thing).  The data still has to be sent in the network, so it doesn't fundamentally improve scaling to be more efficient here (just a constant factor), but it gets block size pretty much entirely out of the critical path for miners.