so the movies should have brought in young people with new character names in 1979.
Which, of course, was the intention of ""Phase II": Decker, Ilia and Xon. And later movies (when begun, ST II was to have been a telemovie) adding a male "Dr Savik", who became the female Saavik, and Kirk's son, originally Dr David Wallace (his mother was from "The Deadly Years").
From the TV series, they should have kept just Kirk, Spock, McCoy, and Scotty-- both for plausibility and because they were the best actors by a mile.
Well, the biggest problems during the "Phase II" planning: Shatner would only agree to sign for the first half-season of 13 episodes and, if his movie career had taken off, he'd have backed away to semi-regular guest spots in later eps. And Nimoy was steadfastly refusing to sign. It took Robert Wise, a feature film upgrade, a pay-off for previous neglect of misuse of his Spock image (ie. the Heineken beer billboard - see https://www.google.com.au/images?q=H...g&ved=0CCMQsAQ
) and a "favoured nations" contract to win him over.
The rest were brought into "Phase II" because they all had their own fan followings - even Grace Lee Whitney was being brought back - and the thought of a "cast reunion" was how the new series was gaining most of its publicity.