If you haven't seen it, watch William Shatner's documentary "Chaos on the Bridge" about the creation and first season of TNG. It's a really good peek behind the curtain.
There's a section discussing the casting of Picard and they had the story of Patrick Stewart coming into audition. He was apparently teaching an acting class at a university in California when someone on the production staff noticed him and thought he would be good for Picard. But knowing that Roddenberry wanted someone with hair (there was some mention of Gene's future utopia having no baldness anymore), Stewart had to have a toupee fedex'd from England. so he comes in with the toupee (which apparently looks awful) and reads and he isn't very impressive so they thank him and dismiss him. Stewart gets into the hallway and thinking he's just blown it, he pulls the hair off his head in frustration. But then someone in the room wants to give him another chance because he/she believes Stewart is the right choice and they bring him back in and for whatever reason he's much more impressive this time. Then Roddenberry's hair objection comes up again and one of the other execs says something like "wouldn't it just be that in the better future nobody cares about being bald?" or something like that, and Roddenberry's original objection is basically overwritten from there.
Seriously though, the whole documentary is extremely fascinating. It's a lot better than Shatner's other doc where he just interviews the various other leads from the different series (aka the one with the segment where Avery Brooks seems like he's higher than a space shuttle and they just dick around on a piano the whole time)
I've said it before, but Gene Roddenberry's contributions to the success of Star Trek are vastly overstated, in no small part thanks to his own engineering of events. He created a great framework, but a lot of the things that people love most about the series have come from the minds of others that worked on the show (Gene Coon, Bob Justman, DC Fontana, Rick Berman, Michael Piller, Brannon Braga, Ron Moore, etc). In fact, it seemed like a lot of times people had to fight against some of Roddenberry's more outlandish, backwards, or straight-up bizarre ideas just to keep Star Trek from doing something that could sabotage its success.
This looks wrong beyond compare.
I do remember that they wanted Saavik to be the traitor for impact purposes. I believe that Alley was unavailable (I can't remember if this was in the middle of her run on Cheers or not) and that someone on the production staff (Nicholas Meyer? Would make sense given he directed Alley in STII) wasn't a fan of Robin Curtis' performance in STIII. I think there was also discussion that someone (it might have been Roddenberry, though given his health at that point in time perhaps not) was hesitant to pull the trigger on traitor-Saavik out of fear of fan reaction given how popular the character had become.
I swear I also read somewhere that the romulan angle was intended to be transported over to Valeris when they crafted the new character as a replacement, but now I can't find any evidence of that and I might just be combining elements of the two character stories into one.
Regardless, it would've made Cattrall's performance a lot more understandable