The weird thing about Valeris/Saavik is if anyone's seen the drafts of the script where the character is still named Saavik, there's no real dialogue changes - Saavik is introduced in exactly the same way as someone who did really well in graduating from Starfleet.
And I did like Kim Cattrall as Valeris. Sure, having a character from earlier movies might have had more emotional resonance, but she really worked in the role.
In TNG, there was also "Conspiracy".
Whose story originally dealt with an actual
conspiracy and only became about space aliens infiltrating the brains of Starfleet personnel because Roddenberry wasn't a fan of conspiracy plots.