For utilitarian purposes, a decent rack trunk secured to a good rack is an excellent solution. But since OP explicitly stated that he's looking for a classy way to attach a saddle bag to a Brooks B72 (which is, if done properly, also an excellent utilitarian solution) I don't think that's what he's looking for.
A rear rack does not serve well as a saddle bag support. I've tried it.
Exactly. Someone must make a decaleur or some kind of classy looking support for the B67.