"This is not rocket science -- it's the preferred way of handling X connections -- but as far as I can see D-Bus is incapable of it. Am I wrong?"
Can you explain how SSH can be used to forward Unix sockets other than X11's?
I have been looking for that for years but never found any example on how to do that.
Since it works for X11 it can't be rocket science but so far all indicators I've seen say that SSH is incapable of it.