Mods might be the best answer. Using commercial game engines to design an educaitonal game seems sensible. The likelihood that librarians or educators could create something comparable to the games students love to play is very slim. So, why not use a Mod (modification)? A colleague of mine has directed me to the game Neverwinter Nights. There are some current academic projects on the go using this game engine. See MIT & University of Wisconsin's "Revolution": http://gaming.mit.edu/revolution/ or read about the University of Minnesota's School of Journalism and Mass Communication's project.