Why couldn't the director just hire a new actor to play the part of the main character? Was Ellen's contract that ironclad? I know it would be weird, but certainly not as weird as forcing a trans subplot on the audience and re-writing the entire season - under a truncated schedule, after they'd already disbanded the writers' room.
This must be a pretty unprecented situation the show runner finds himself in. Imagine if your lead actor premeditatedly trooned out, without telling you, leading to months and months of wasted work and time. Then, you have to act supportive and pat said actor on the ass for their "bravery," all the while pulling your own hair out from the extreme agitation and stress they've just wrought upon your world. 2-week family vacation to the tropics, before shooting starts, after you've just slaved for months, bickering with clueless execs and the writers, getting a script together? Yeaaahhhhh, I'm gonna need you to throw everything in the trash that involves your main character. You've been forced to cancel your plans and, hurriedly, rush together untold amounts of rewrites into the script. Everything pertaining to that character must be gone through with a fine-toothed comb. Was someone supposed to look at your lead with disgust in a scene, after they make an off comment? Well, now they're a troon and Hollywood can't have that. Now you get to completely re-tool that entire interaction. Hopefully that interaction doesn't affect any part of the plot, because if it does...that's another scene to rewrite. Also, you must write a whole new subplot to placate your star actor for cutting their hair and lopping their tits off, while everybody tells you how great and brave this walking ball of self-obsession is.
Then, that season sucks and the director gets to listen to everybody tell them how much they've fallen off. What a fucking nightmare.