Schwarzenegger and Clarke actually had good chemistry in the gun-loading scene.
They'd do well as a duo struggling to figure out what to do about the Saranator.
And, given how much of John's personality seemed intact--albeit twisted--in the TermiConnor, the Saranator might be fun to spend time with too.
Some of the most fun films are the ones where we get to see the struggles of the villain as well as the heroes.
'cause we still like her and want to root for her.
So... yeah, missed opportunities. A lot of great ideas, but they couldn't all fit together in one film.
A film about John Connor become a Terminator so Sarah and Kyle have to hunt him down, OR a film about Sarah Connor and Kyle Reese having their roles reversed, OR a film about Skynet seeking to become more human and instead going crazy. Not all three at once.
(Personally the last is the weakest link. "AI seeks to become more human" is not a BAD story, but it's been done so many times, and almost always exactly the same way. Skynet is not Pinocchio.)
Hmm. New idea for a trilogy:
- First film is Sarah and Kyle with roles reversed. Old T-800 is her father figure, they stop Terminators and prevent Skynet, it's all fun and games in a glorious homage to the original films.... and in the midroll credits John Connor time-travels in, all Terminator-y.
- Second film, John TermiConnor shows up to protect the nascent newest iteration of Skynet from Sarah and Kyle. The reunions are tearjerking, and maybe TermiConnor kills Kiddie Kyle to show how he's a bastard who's immune to timeline change. They trash him and stop Skynet again! ... but Sarah is infected and it closes with T-800 and Kyle searching for her to try and stop her. Midroll credits: Sarah starts building a new Skynet.
- Third film: T-800 and Kyle on a hunt through time and around the world for Sarah Connor, while also trying not to get killed by her agents. They team up with a pre-infection John Connor and causality goes to cry in a corner when they're unable to stop Sarah from causing the Skynet Singularity, but they purge the pre-Skynet past of Terminators and travel to the future where they destroy the time machine so the victory over Skynet is complete.
Humanity will be subjugated by robots, but will triumph in the end.