Gopher by itself is actually not hard to extend, as far as people standardize on how to extend it. That is why most of the discussions on "gopher enhancement" never resulted in big changes. Several ideas must be spread across the gopher project mailing list (now hosted at alioth, see archives at gmane), and some of them are quite good. The only consensus, though, seems to be that any extension is going to be done over plain gopher, not gopher+.