Oh, good call, @fallenj!
I'm guessing this won't work then. I loaded up my single-player save from right before Karlach's paladin encounter, and connected 3 other instances via LAN connect.
On each of those other sessions, the player is greeted with the character creation screen, and the only option available to them is to create a custom character. ALL of the Origin NPCs show a padlock symbol with a mouse-over tip reading, "Not available when joining a running session."
Screenshot: https://www.dropbox.com/scl/fi/wxqp...rlkey=jt9hepwgv2cfr08apxh0nl5b7&dl=0Oh well, guess "Jim" will just have to miss out on the Origin NPC hijinx. Such is the sacrifice for doing one's part to ensure the continued existence of the human race...
EDIT: And yes, as is well-known, once a player leaves the party, their "Tav" remains in the save game. Glad I backed-up my save folder before trying this! ^_^;
Screenshot: https://www.dropbox.com/scl/fi/4qd5...rlkey=90ejh2gdhgbrao1xaqw2q9y3g&dl=0