It would be possible to use a csv file as an input parameter with a few changes. Python has a csv reader/parser module that could convert a csv to a list which could be iterated through.
13.1. csv — CSV File Reading and Writing — Python 2.7.10 documentation
A few changes I would make are removing the loop for the 3 scales, I was going to just have it set first scale, save, set second scale, save with new name, set 3rd scale, save with third name. Other thing was to add field delimiters so you wouldn't have to change the select by layer expression depending on which input type you are using, shapefile, gdb fc, or sde fc.
http://resources.arcgis.com/en/help/main/10.1/index.html#//018v0000006p000000 (copy/paste)
You wanting to keep it a script tool, or just run as a python script?