Well create metadata resistant protocol that communicates on set intervals of time with set length of random data when there is no real payload. This could be done on TLS with little or no effort. The math behind the crypto is strong enough. No need to harden it further.

Every client sends and receives 16KB blob every 30 seconds - this way you could prevent analysis that you are communicating with someone. You could learn a lot just from the size and frequency of packets in a normal chat program.