@Heiner > I'm the kind of DJ who does all that "tidying" before I import it to my DJ software. I edit my tags, run any other processing (eg. MiK, Platinum Notes), put the files in the appropriate folders, then import. Anything done within the software after import would be to add tags, sort into playlists, etc. - the physical file doesn't need to move.
If you're the kind of DJ who moves his files AFTER the import, the link to that file will be broken in the database. It need to know where and how it moved in order to play it. Think of it this way -- walk into a library (you know, the kind with physical books) and pull any book off the shelf, move it anywhere else in the library, and don't tell anyone. That's basically what you've done when you move a file on your hard drive. The book still exists in the library, nobody has checked it out and removed it, the computer listing still shows it as available, but unless someone went searching the shelves, there's no way it would be found.
You could use the relocate missing files function, but this is mostly for being able to relocate moved files, not renamed files. Per the library analogy, this would be akin to moving an entire shelf of books to elsewhere in the library. That would be easy to find, and once you have found it, you can update the location for ALL books on that shelf.
But if you've done more than move the books, say you created a new dust-jacket for it, nobody would know WHAT they're looking for. If you did that more than once, and again, didn't keep all those books together, it's going to take a LOT longer for anyone to find them, and re-catalog them all.
Our engineers do care about this, but to be perfectly blunt, this seems like a poor practice in file management and some small changes to your workflow would be more effective in reducing the amount of effort anyone needs to make.
Oh, and regarding taking your drive with you ... if you keep your music ON that external drive (as the source), then you export to the drive, it doesn't make duplicates - it points the export database to those files, so you could feasibly maintain a folder structure and not worry about how rekordbox creates its ridiculous export folders, and do what you do, as you need to.