I've had the same notion since seeing Paris, Je T'aime.
I've been working on full SPs so haven't had a chance to really think about it yet, but i think it might be a fun exercise at the very least. I've never written a short film script... so writing several revolving around one theme would be a challenge for me.
Are you familiar with an exercise conducted by Mystery Man on Film? http://mysterymanonfilm.blogspot.com/
I vaguely remember him having several aspiring writers write a short script with the theme of "Love", and another on "Hate". One person could do the same thing by themselves.
I can't speak to the marketability of something like this. Maybe some people in the DV indie scene would be interested in a (small scale) collaboration. (??)