Since 7-Zip's GUI still doesn't have the option to "compress each file/folder to separate archives" like WinRar has, we have to do it through 7-Zip's command line.
So, here's a batch script that does just that.
After using Zandro's batch scripts to sort all your roms into their proper folders for their respective sets, use my batch script to max compress all of them into separate 7z files. (At least I think the settings are max compress--it's been awhile since I read up on 7-zip's command line and wrote this simple script)
WARNING: My script does NOT delete the roms after compressing them, so make sure that you have enough HD space for the entire compressed GoodSet. After compressing, you'll have to manually delete the uncompressed rom folders yourself.
Also if your computer has less memory, you might not be able to use the max compress settings. In that case, you'll have to open my script in NotePad and edit the values to ones that your computer can handle.
WARNING - Pt. 2: For really large rom sets like the Super Mario World hacks (~2 GB each) in GoodSNES, you're going to need a lot of memory for max compression. If you don't have enough memory, then the folder will FAIL to compress and be archived. Unfortunately, my batch script won't inform you of this. If you then delete the folder thinking it's been compressed, YOU WILL LOSE THOSE ROMS.
So, before you delete those folders, make sure the roms have in fact been compressed and archived.
Sorry, but I don't know how to code the batch script so that it will stop and warn you if there's not enough memory to archive those larger folders. I'll try and look into it.