I wonder if containers on the desktop would be useful for this kind of situation. You could have containers for different distributions, or even different versions of a distribution. For example, one for Ubuntu 14.04 and a different one for 13.10. The containers wouldn't do much, other than take up filesystem space, until they're needed.

This wouldn't work if the software requires a kernel module that isn't packaged for your distribution. It also wouldn't be particularly useful for a file system navigator or something that needs to see the rest of the system. That should still leave in quite a bit of useful software.