Anyone who played Guild Wars for any decent amount of time knows what this is, and cannot deny that it was, in fact, a good implementation of microtransactions.
And I implore Arena Net to take a look back and consider re-adding this type of content for Guild Wars 2.
For anyone who doesnt know: http://wiki.guildwars.com/wiki/Bonus_Mission_Pack
To summarize the Bonus Mission Pack, they are miniature story missions that fill in and spread into various parts of Tyrian lore, providing new content for players, as well as rewarding players with unique and interesting skins.
To think of how Anet would implement this, there are just so many things they could possibly do.
Recreate missions from prophecies, nightfall, eotn, and factions to add, fill, and even create lore, while giving older players nostalgia, and new players information and that feeling of “brand new” while still being old.
Adding a vast number of weapon and armor skins, from the unique skins from the token rewards at the end of each GW1 campaign, to sought after skins found in the original Guild Wars and its Bonus Mission Pack, to brand new skins letting the creative designers in the company shine even brighter.
To parallel the “living world” of Guild Wars 2, with a more “history book” approach in telling players a story, I believe it would be a great addition to the games content archive.