As I understand, system could distinguish one external storage from another. So, I think it would be useful to set unique after-plugging-behaviour for each device.
For example, I use 4gb apacer flash only for backup. So the only thing I want to do with it is to run appropriate script and then unplug.
Another my USB device is my 2gb transcend pleer. Every time I plug it, I want only to sync contents of my ~/music/2pleer/ folder with it. So, may be you could find some solution (preferably GUI-based) for this?