Re: HPN-SSH
Maybe you could reuse this https://www.psc.edu/hpn-ssh-home/hpn-ssh-faq/. They say: "... is fully interoperable with other servers and clients. In addition HPN clients will be able to download faster from non HPN servers, and HPN servers will be able to receive uploads faster from non HPN clients..."
This has been partially implemented already:
https://winscp.net/tracker/17