Though apparently it didn't take all that much compression of season 4 - Intersections in Real Time was originally supposed to be either episode 4.22 or 5.01, and instead it was something like 4.18 (too tired at the moment to check it at the Lurker's Guide). Of course, there would probably have been a few more episodes between it and Clarke's defeat, but it was likely going to be something like what happened in season 4, when they resolve the Big Issue by episode 6.KenM said:The problem JMS had was he thought season 4 was going to be the last season, when he planned for a 5 season arc. So he had to try to wrap up the major plot points of the show in 4 seasons, not 5. He changed some things around, thats why season 5 was so weak, IMO.
I think a far greater reason for season 5's weakness was that Claudia Christian left, so instead of having Ivanova advance to fill Sheridan's shoes as Captain of B5, they added Lockley. AFAIK, the original plan also called for Ivanova to be the one who got romantically involved with Byron, with Lyta being more peripheral to the teep movement.