On the idea of replacing the leads with presumably cheaper cast members … I note that David Gerrold wrote an amusing short story for the anthology Alternate Kennedys --- a collection of alternate histories based around the Kennedy family. In this story, Joe Kennedy stays in Hollywood rather than getting into politics. The result is that when Star Trek is squeezed between budget pressures and production pressures, particularly Shatner and Nimoy feuding to the point they can't reliably produce a show at all, the brothers John and Robert Kennedy are well-positioned to replace them for the last season of the show. It does offer the chance to tweak the format of the show to smooth out some unrealistic touches and maybe open some new storytelling avenues, but, well, you think we have fanboy nightmare outcomes in our timeline …