Hi
There exisyts a new interface in Wireshark, called extcap. It is a plugin interface, which allows you to use self-written programs as capture interfaces. So far the interface is only in main, but if you download any 1.9x version, it should be included.
This would allow you to write a program, which acts as a ssh-remote capture tool. Multiple instances of those interfaces may be used together, so you could, in theory, implement your scenario. Synchronizing the captures would be a totally different task altogether.
Documentation is not yet complete for extcap, but there is a basic python demo program in the ./doc folder of the current wireshark source tree.
regards,
Roland