Just a suggestion..
*Edit* while thinkin about this, I though of another suggestion on the same Topic...
how about a blacklist?
lets say I have an app that makes justalog.log in C:\Program Files\SomeApp.. if i use the Custom Folder it would delete everything in there. but if there was a blacklist option i could tell it to delete in folder C:\Program Files\SomeApp delete just the file justalog.log or even better allow wild cards... so you can have it delete *.log in that folder.
Just another suggestion..