I was just looking into some "replaceable derailleur hangers ". It should be done on a Mill but I see no reason that one of these could not be retro fitted to fix this problem.
Yes, it's possible. I've heard of at least one person who found a replaceable hanger that would fit the shape of his existing dropout, and subsequently had the dropout thinned where necessary to match the pattern of the replaceable hanger.
Expensive, tedious job, but worth it - especially when the result yields you a nice period Cannondale that will never have this problem again, so long as you can source replacement hangers.
-Kurt