I know the SOCKS5 protocol and how to implement it in C++. The standard
is fairly easy and there's also a reference implementation in Bitcoin-Core.

Would this be a useful thing for me to implement and submit to
libbitcoin-network? Basically does the SOCKS5 handshake so the connect
is initiated and ready to work over Tor.

The usecase for having a server running over Tor is 2-fold:

1. You don't want a passive observer to know you are running/developing
Bitcoin applications for safety reasons.

2. Reduces the ability of targeted attacks on servers. Sybil attack .etc