One of the things the hurt The Undiscovered Country was the replacement of Saavik with Valeris and all the goofball humour that came with that change.

The look on the engineering hand's face as the top graduating officer manages to get the ship out of space dock is very silly.

She's top of the class but can't steer?

Having Saavik as the turn coat would have been much more dramatic and like Kirk she had good reasons for not trusting the Klingons.

It would have made the mind rape scene between her and Spock more unpleasent too (especially if she did have a child explaining her stay on Vulcan in The Voyage Home).