The ranks reflect rank in realms. All rulers and dukes in Terran, Barca, and D'Hara are entitled to elderships. All council-level posts are entitled to full membership. Lords and below are applicants.
Problem with guild treasuries is local taxation: taxes sap out a big chunk, allowing the local duke to accumulate vast surpluses (case in point: me). The only viable banking institution is one that can readily accumulate assets, such as through favorable tax status and alternative income sources.
Oh, yeah, a religion.
