And yet this was done with games in similar situations (most applicable to everquest) so it is obviously not something that is impossible. For the bugs, being that it would be using a previous or even current build of the game the bugs would be minimal. As for the age of the playerbase, a lot of people who played the game BACK THEN were in that age range and managed just fine so I am not sure why you would assume that matters especially since if they don't like it its only a server option?
Finally, in response to it getting them no money that is just flat out incorrect. If that were the case then why do we have patches? The mmo industry is a "service" industry and offering options such is this is a service that will help to keep players or bring back old players or even possibly bring in new players.