Would it be possible to have an online agent database (such as the Uplink Directory, http://uplink.stewsburntmonkey.com/) where agent data is posted and all the Uplink agents within the game are created from that database?

The database could contain names and details of members of the community which are submitted via the Onlink website.
I assume posting photos and displaying them within Onlink would consume vast amounts of bandwidth, so it would be impractical to do so.

It'd be so nice to have people in the game that are from the game community.

Wouldn't work as a selection of people don't play while online all the time.

I'm guessing the details would only need to be downloaded when you wanted to update them and thus you wouldn't need to be constantly connected to the database.

The point of whether somebody is connected or not at any given point in a game is irrelevant.
The characters are generated when a new game is generated, and it would be very annoying to have new people added to the game when you update... especially in missions if the credentials of the person change. The only time that the character database would need to be downloaded is when creating a new game. There should be an tickbox on the options screen to say "Download Onlink Community Player Database on New Game", so that if the player's computer isn't internet enabled, or it's just not dialed in at that moment, the download feature can be switched off.

I can't wait to be framing certain people for stupid things... you'll all be doing it. ^_^