This would seem to me to be best solved through the use of multiple guilds. A "trade" guild doesn't need a "military command" branch.
Guilds are intentionally not mini-realms. They are focused groups with special purposes. We don't want them to replace realms, or to serve as a multi-realm control structure. Cross-realm communication and coordination is intentionally more difficult than in-realm communication/coordination. If you want to set up multiple channels of communication like that, in order to allow coordination on multiple topics, then you're either going to have to deal with the inconvenience, or go through the expense/difficulty of setting up the multiple guilds/lines yourself.
Another use case would be a guild that represents a federation. The federation-guild's elders would be rulers, but they might want a separate channel for generals and marshals, and a separate channel for bankers and traders.
