I'm sure I'm not the first too think of this, but this would be the coolest thing.... Its as simple as an add on control... You link a useless item in the game to a double click cmnd.. Example: a Grey loot item in World of Warcraft, a crafted fork in Ultima Online, Once configured, you seamlessly go through a portal and zap are logged in, and playing on a linked character from what ever game you linked to that item. You should be able to seamlessly go back and fourth between multiple games, ideally any online RPG game you played this would work with...
A World to World Quest Line.... Example an add on that detects what items your characters in Ultima Online have. You get a quest in Shroud of the Avatar with any charcters that have the same name as charaters to chosen server on Ultima Online, that gives you credit for items that you have in Ultima Online or any other previous version of the Ultima Games... Also.. Updated Arcade Emulator that can play all the Ultima Games Sold as a packaged Gold Set for Say $60...