It's interesting, but I'm curious, had Spock stayed dead and Saavik took her rightful place as his replacement. Would Alley's higher salary demands for Trek III have been fulfilled?
I always get the feeling that Director Nimoy was behind the "clean slate" for Saavik. Paramount supposedly offered Kirstie Alley less for ST III than she made on ST II with the reasoning that "sequels traditionally make less money". Naturally, her agent made a counter offer that was ridiculously high (equivalent to Shatner's salary, I heard), fully expecting the
counter counter offer to be something in between. The agent never received a call for renegotiation. But, contractually, Paramount had fulfilled its responsibilities to Alley by making an offer. And that was it. Had ST II not been Alley's first job in Hollywood, her contract may have been more specific about salary potentials for possible sequels.
They didn't bother fighting the situation because Alley suddenly got offered a lead stage role in Los Angeles ("Cat on a Hot Tin Roof", IIRC) and, for a young, up and coming actress, having a well rounded CV is far more important than repeating a role in a sequel film. (This anecdote came to us from Bjo Trimble, who'd talked to her not long before Bjo did a convention in Australia just before ST III came out.)
With Alley gone, Nimoy joined in the search for recasting, and molded his new Saavik into a rather different character. Had Nimoy opted for Spock to "stay dead", ST III would probably have developed a film or telemovie where Saavik and David were the leads, with Shatner as the top-billed admiral, expecting Spock-like performances from Spock' protoge. Whomever from the rest of the cast signing aboard would round out the experienced crew, but they may have populated the ship with young people (or at least the age of TOS crew members!)
With the SPFX guys still complaining about the TMP shooting model, there probably still would have been an attempt to replace the Enterprise with a different ship at some point. Maybe something more suited to a fledgling, acting captain and her non-Starfleet scientist/specialist? Maybe a
Reliant repaint to save money?
Note also that ST III was written without a clear indication that Nimoy would actually decide to return as an actor, or just director. At the very last minute, he could have changed his mind - and Maltz simply would have beamed up Spock as one of the previous, younger actors playing regenerated Spock.