JMS even wrote about 60% of "Crusade", and I believe most of the movies were written by JMS.
He wrote all of the TV movies. Of the produced and aired Crusade epiesodes, JMS wrote 10 of the 13. Two more JMS scripts were completed but not produced. Fiona Avery wrote two of the three produced scripts by other writers with Peter David writing the third. There were three scripts assigned to other writers but production was halted before most of them were finished. A spec script written by Peter Woodward would have been made in the second season.
For those interested in the unproduced scripts, you might want to check out the 'Crusade: Other Voices' books which are still available here.
Volume 1 features the Peter Woodward script and Volume 2 has early drafts of the Avery scripts as well as a draft of one of the assigned scripts by Richard Mueller. (Full disclosure: I'm part of the team that puts out these books but I don't have any financial stake in them. I just think that the history is important) Eventually, the two unproduced JMS scripts will be published in the rest of the 'Crusade: What the Hell Happened' books.