An idea on rares

I know the thoughts on rares is that they should be implemented but no one knows how to make it fair. My thought is to have 1-2 days a month where every clue had a minuscule chance Of dropping a rare, like .001%. I think this would limit the ability for people to get rares, but still have it be accessible enough for them to exist. This wouldn't apply to level one clues as they are too easy to complete. Thoughts?