Well any reprints of Death of Superman/Reign of the Supermen should still include the GL part of the story as Hal showing up was a bit pivotal to the outcome.
However that doesn't mean they NEED to put Gerard's name in the credits with the rest of the writers/artists.
As to the rest of his work, well if it isn't in demand then there isn't much to worry about. If they want to release TPB's of that era, just remove his name from the credits.
I guess I don't see the problem from a larger view.
There are a lot of creations, scientific breakthroughs, music, football stars etc...that can be called on what they did wrong held accountable for it without re-writing history.