Why you don't get rid of the "Scale Interface" option and create unique proportions for each resolutions, with a .ini file inside each interface folder.
Like this:
1920x1080=100
1280x720=75
1024x748=60
etc
=number mean the proportion (%).
Why I'm suggesting this? I'm playing with 1080p and everything looks giant. When I turn off Scale Interface looks like I'm playing
Action Quake with these small texts. I think that something in the middle of both would be the best for 1080p, but I can't customize that, right?