You can relocate the masters as well as export them. It's trivially easy to do so.
I was faced with the fact that I had about 400 directories that I wanted to rename (I originally imported as YYYY/MM/DD and then I figured out in Lightroom that stunk as using the rapid project manager just showed DD and thus I couldn't use it reliably). Trying to rename those 400 directories in Lightroom was an impossible task, where in Aperture I could do it in about 5 seconds.
Just for future reference, one way of doing what you wanted would be to drop from LR into the Finder, use something like Name Mangler to change the names and then, back in LR, synchronize folder.