relative paths or working directory selection
We use a SVN repository to store, version and backup our models. This generally works well until we need to pull up old versions. Since the parts have the same names, the system will open up current files instead of the versions downloaded from our repositories. If you don't notice that this happened and save, it can wreck models.
Give us the option of having relative paths or a starting working directory. As long as the main assembly is only looking relative to its location, it won't pull in other versions.