I really don't think I've encountered anyone who hated Chiana as much as you (or at all, at that matter). It's quite interesting, as I can actually see why someone might find the character grating (but I always loved her and felt the first season picked up a bit with her addition, so there's that.)
The Deadshirt - That's oversimplifying, since JMS condensed the plot arcs he planned for both seasons four and five into season four and then got picked up for a fifth season on another channel which resulted in a season that dealt with a ton of unplanned material... and that would be ignoring the way his plans for the show's future shifted radically over the years to the point the initial arc envisioned when shooting "The Gathering" is practically a different show.
When did S5 get 100% condensed into S4, certainly before the fear of S4 cancellation. To the best of my knowledge, the S4 Cancellation cost was the final Four or so episodes of S4 were supposed to stretch some things into the first four or so of S5, while the new Arc Elements that start cold at the beginning of S5 would've started slowly, more organically at S4 tail end to take their place so there was a smooth transition between seasons, rather than a Babylon5gasm at the end of S4 and a cold restart in season 5. And of course, the Actor who left had to have their arc redistributed to other characters.
One Day I hope to be the Man my Cat thinks I am
Where are we going? And why are we in this Handbasket?