fair use through dual licensing?

I've been thinking of the "fair use" issue, and I've come up with an 
idea which I'd like to run past everyone.  Why not have users dual 
license their text under the GFDL and Creative Commons by-nc 
(attribution required and no-commercial use, with derivitives allowed).  
This would allow Wikipedia and other non-commercial entities to continue 
to include "fair use" images, but it would require commercial users to 
release their modifications under the GFDL (thus they could still use 
the public domain images, but not the "fair use" ones which they were 
probably not allowed to use anyway).

Additionally, make a "public domain" checkbox for submissions, certainly 
for images, so this information can be easily scanned.  Strongly 
discourage non-PD (and non-GFDL) image submissions, and try to replace 
what is already there by clearly-marked public domain content whenever 
possible.

Oh, well, just an idea.  Feel free to ignore, flame, agree, dispute, 
spindle, mutilate, or whatever.

Anthony