Using a binary protocol looks to me like a premature optimization because you sacrifice all the advantages of a text-based protocol and buy in pitfalls. Just because you want to have more TPS although the current way is much faster than Bitcoin itself.
Half of the protocol is binary already. Transactions are converted to byte array, then byte array converted to hex string, then that string is passed to JSON. Most part of data is byte arrays anyway: hashes, signatures... AMs is byte arrays completely. JSON is just overload, IMHO.