An argument is often made that the original creators would have done this or that given better resources such as exist today. Well there's no real way to know what they would have done. And given their perspectives during the '60s there's a damn good chance their choices (with better resources) could have been quite different than what was done with TOS-R simply because they wouldn't have been influenced by forty years of subsequent modern sic-fi in film and television as well as Trek spin-off films and TV series.
Jefferies may have given his blessing, but he too was influenced by the intervening years. No one can know what choices he might have made if better resources had been available in 1964-69.