I would like to claim responsibility for this idea, but, in truth, I got the idea from a real life/real-time role-playing effort that is done near here (everyone plays their characters themselves, in costume - there are rules for magic and fighting which allow the effects while keeping the players safe), and its just somewhat modified by Ratatouilles ideas in the Role Play Quests post.
It should be possible, with only a little effort, to put together real time tiny plots for the imms to play. One of the disadvantages to most staff positions is that you learn too much about the things that are hidden from the players. And, as most immorts used to be players, I believe that most of them would like to continue playing on a level that fits their experience and knowledge.
Moreover, such a quest would not have to be run by an immort but would have to be assisted by, probably, only one. The mobs in this case would be players. The point of the quest would not be x.p. or treasure (although, having an imm code up something wonderfully unique for the winner might be fun even if it did nothing at all). Players and administrators would not be giving any points to anyone. The point of the quest would be simply the playing, figuring out puzzles, winning the quest.
To set it up, someone (player, imm, Bob the plumber, it doesnt matter who) would design the basic idea for the quest along with the number of computer-mobs and/or player-mobs required and any special items that might be required. Obviously, to install computer-mobs and special equipment an imm would be required. Players would be involved to give the game the flexibility that a computer mob cannot have without some extensive a.i. It would not even be necessary to create special mobs for the players. For the most part, they should be able to play themselves. The only addition might be special equipment which would, of course, be taken away after the game. In the rl game I mentioned above, player assistants were given a fixed amount of pre-determined xp for their help. That would be nice here but is probably not necessary.