I have not played around with RDX to know; does it support frames for the guild bank frame? I imagine it does, along with the player's bags, and probably alt characters as well.
Anyway, if RDX does support a guild bank frame, I was wondering if you could or would support either LibGuildBankComm-1.0 or a feature like it? The lib scans the guild bank while you are there, taking page permissions into account (if you can't see a page, it won't scan it), and sends the data in compressed, serialized format to other guild members. Once they get the data, their copy fires callbacks allowing installed addons to update the guild bank without them actually visiting, again taking permissions into account. If a player's guild bank permissions change up or down, the lib adjusts, and should the player lose view permissions, nils the appropriate data.
Curse and WowInterface downloads, where you can read the pages and see the APIs and examples.