Did this a while ago, but never got around to actually using it, although I did implement the functionality on QO (i wanted to be able to easily communicate between our main and test server). Basically servers themselves communicate with each other (limited to spawn/jump/walk/run/chat) packets on a single map (agreed upon by all servers involved). And then rebroadcast those packets to all connected clients on that map, effectively giving a "meeting" area for interserver chat.
There are some problems, such as duplicate names and player IDs, but if any of your other non-binary pservers would be interested in doing something like this, I'm sure we could agree upon a common protocol easily enough to overcome any issues.
There are some problems, such as duplicate names and player IDs, but if any of your other non-binary pservers would be interested in doing something like this, I'm sure we could agree upon a common protocol easily enough to overcome any issues.