Aye, I'd like this as well. A manual way to drive people from one synth to another.
You might like to look at what was done with the sets of Stargate Universe in terms of linking from one synth to another. It takes place outside of the synth viewer, but it's fairly similar. For example, check the second highlight on the first synth to find one of the links to another synth.
Also, I'm not sure what you've read regarding the Photosynth team's plans for linking synths, but they should provide the sort of scenario that you describe in an automated(ish) way. I hesitate to link to my old post yet again, but it is one of my better information harvests and about a question that gets asked quite a lot, so here goes.
I'm assuming that using the geo-alignment tool on all your synths is setting the course straight for whenever linked synths are finally released.