I think I like this idea. I can't say if I'd use it or not until I see it in action.
the choices you've listed seem pretty comprehensive, and I'll need more time to fully consider any missing choices. I'd also be expecting the list of 'common searches' to be editable. We should be able to remove those we won't use, and add any we feel might be missing, or edit existing ones that might need a little tweaking.
re. searches such as images from this month, images from this year etc. etc.....
These stock smartlists in current versions are misleading. audio imported today, for example, really means "audio imported in the past 24 hours" which means it often lists audio imported yesterday.
I've got an 'images imported this year' view scheme on the go here already, but, come the New Year, I'll need to edit it so that it pulls pics from 2007, not 2006.
If you can find a way to make these searches do what they say on the tin, there's more chance I'll use them. I'm guessing the only way to do that is to get the date from the system, and then base the smartlist around that, and I'm not sure if that's possible or not.
-marko.