Nice idea, didn't test it yet but I'm sure it will help as my printer has a quite basic system for fixing its belt and it's really hard to get them tight.
Just one little thing, the .stl is little botched and my printer (using cura slicer) prints it in a quite bad way. Check the wireframe and you'll see.
Great and nice that you provided the source though, I just advise people who are able to read the file to re-export it themselves.
Thanks for this neat part :)