Never even seen the books, but I'd love to give it a swing. Actually I don't think all of the stories for B5 have been told. Although I would probably have to drag the players off the station after a while the universe is just to big to contain all of the little plots and schemes going on.
Between the Psi-corp, the Rangers, Vorlon, Membari,(yeah I know I probably butchered the spelling oh well) and all of the rest. There is still a lot of potential for all of the behind the scenes players. I think I'd play it as a military/espionage setting. lot of fun!