Actually I have a workaround, but I have to start using multiple MIDI Ports in GS4, and they are not capable of switching back and forth to unless you click it with a mouse.
It's an 8 port MIDI application that can load 128 libraries via 8 ports, and 16 channels pre port.
I will simply use instrument stacks on seperate ports until the XTDM options are a reality.
This way of port switching is a simple mouse click, since all of the content is preloaded into a project, I will just use 1 of the 8 ports where the instruments are stored to suite my particular needs for the song / performance.
It would require some preparations which I am undertaking as we speak.
For Example:
Rhodes sounds are never used simultaneously w/ a Wurlitzer 200A, so each EP would be a choice to have on a seperate port.
Horn sections, strings, Grand Piano, and Rhodes are mostly used, so on port one they will reside.
This means that the same MIDI channels would offer different instruments of the same catagories on the same MIDI channels, but different ports.
A final example is the strings. I would have the Symphonic Strings, ARP String Ensemble, and Melotron on the same MIDI channels, but different ports.
My particular needs will use channels 7 thru 16 ( 10 MIDI Channels ) x 8 different ports, for a total of 80 possible instrument libraries.
Since I only use 37 different libraries, the extra slots in the extra channels and ports could double certain instruments that are used more.
This is a slight pain, but it only requires that I hit a port number w/ my mouse. No problems loading during a gig, and everyone is happy as I have access to VSTi's hosted by GS4, and all of my synths will be on their own channels in Scope.
But this doesn't mean I am letting Ralf and the boys off of the hook.
XITE-1 customers will be asking for extra AES / EBU's like warp69 has mentioned, and many others have their needs as well.
But as our beloved Spock once said.............................................