...Would have instantly made it a better film.
Though this depends on them having actually gone on with the Saavik is half Romulan sub-plot.
The big missing link in Valeris's arc is motive. While being half-Romulan doesn't inherently make her a traitor, it does offer reason as to why she might
do it. And having her as the "new guy" just weakens the whole thing even more. But then I suppose it's better than if they had made her a red herring.
Of course, the plot (in whole) is missing a motive. The "We might lose our jobs because the director branded this motley crew of intrepid explorers a military!" excuse just doesn't fly. At all. The lack of motive is really the only thing that held the film back from being one of the great sci-fi films of all time. And the gravity boots.
Also, head of security not securing.