The problem I see is that if it's an automatic inclusion people might expect the comm mod(s) to list and tag appropriately - which means they have to read the fic to do it... probably need more than one mod, and not all from the 'need warning' group of readers.

Also, absence of a story from the warning comm list might not mean there are no warnings for the story:P

It's still a very good idea, thanks due to ladymeander, and I'm sure these things can be worked out.