It's something we may look into after the move to Dreamwidth, but currently it stands, I'm afraid. The 1/3 rule tries to work within the spirit of fair use - it's hard to argue fair use if we allow, say, the entire Blue Beetle second feature from Booster Gold to be reproduced in full. DC would argue (rightly or wrongly, but certainly legally correctly) that they would lose sales from those who pick the book up just for Blue Beetle. The same for any other similar anthology book.
The link above explains the reasonings behind it in full.