Duplicating and renaming Finder selection to the same folder in one clean step?
For your applescript solution, you could duplicate to a temporary directory (preferably on the same file system), then rename them back to the original directory. I tried to hack this together for you but gave up...

If you want an alternative, instead of bash you might look into this answer https://stackoverflow.com/a/275945/1942837 which provides a (presumably) nice python gui with progress (I have not tested this).