1) Not sure of their linking standard, but either a direct link to the GCD, or perhaps some type of webservice call to their services to retrieve information (stories, artist, writers, etc) (assuming GCD even have such webservices available).
2)Standard naming format for all files : Ex...Pub_Title_Issue. I know there is kinda ,sorta a standard, but its usage is fairly inconsistent.
3)As part of the database of titles, have it track all the total number of issues that were published, so all users can see much easier what is still needed. And what lines are complete (10%, 35%, 96% - Missing 16, 35, 87). Maybe this would be an easier trigger to remember if they have something in stock. Or perhaps allow for an automated ebay and auction house search for when titles pop-up, for those generous users willing to purchase.