I use Jamba 0.5 (the one under development) and am pretty sure the functionality doesn't exist yet, but would be very happy to find otherwise!

The characters in my main team are spread across three guilds, two of which contain stuff I actually want to read.

The problem with the guild2guild add-on is that it will connect the guilds together, and that's not what I want at all. What I really want is for guild messages - all guild messages from all characters - to be forwarded to whoever is currently the Jamba Master.