Firstly "The Survivor" features one of the coolest looking aliens ever seen in Star Trek,
a Vendorian. Add to that it's not a bad story and we finally get to see a female security officer, Lt. Ann Nored. The part that threw me out of the story was the bit about the Vendorian assuming the form of the ship's deflector shield.
I couldn't swallow that one even when I was 14 years old. Now if he had assumed the form of some of the shields damaged components then I might have been able to swallow that a little more easily...maybe.
Alan Dean Foster makes this change in the novelization. The idea of the Vendorian becoming the actual shield is highly implausible. As that action takes place off screen all that was needed to fix this was a simple dialogue changed, but I imagine the writer and producers felt having "Carter Winston" become the shield was (a) more exciting and (b) simpler for the younger audience to grasp.