Note, however, that you probably couldn't have any penetrations (i.e., sensors, wires, windows, antenna mounts) on these guys. Not necessarily a bad thing, but it makes them less flexible than traditional rigid bodies.
Thats a good point about not docking the soyuz on the structural axis. Another interesting question would be how to use inflatable modules on future moon missions. You could have an inflatable mission module or landing module, but you'd have to be careful with docking. Also, you could do a transhab style thing with a solid core and fix any problems with that.
I believe they did design a window into the transhab somehow, so I think its possible.
injectable foam is an interesting idea. I'm sure it would expand very differently in space though. Maybe I could submit that to NASA as a student experiment thing.
"less flexible than rigid bodies": no pun intended, I'm sure.