Other people have great suggestions for content. My suggestions are more of under the hood type of stuff, which would make the game have a very long life, especially with expansions, and DLC. Heck, the game can even have a series of modules that are played like a serial (think Ultima 7-9. This definitely will keep the game as a revenue source.
AD&D rules: It would be nice to have 4E or even 5E, but PnP is difficult to translate to computers in some cases.
Servers: It would be nice to have the ability to have multiple servers, with a server acting as a character data server, ar