And about Marcus - was it always planned to have him killed at the end of season 4? I always thought that he and Ivanova had a good chemistry and were geared up for romance, so I'd really like to know whether any real life issues (other than Christian's departure) put a stop to that story arc.
I don't know if there's anything about this in the script books, but JMS once implied in a web post that there was a planned plot to revive Marcus in season 5 that depended on Ivanova.