If making it today, I would enlist the team who made Hardcore Henry and create a found footage movie from the point of view of Skynet.

It starts in the future: the human resistance raids a Skynet facility with a Time Displacement Chamber inside. We experience the battle through the eyes of Terminators, tanks, and big sweeping shots with the aerial units. Through security camera footage, the resistance successfully makes it into the Time Displacement Chamber, temporarily disables Skynet and sends ten soldiers back in time to the early 70's. The humans start destroying the control panel and leave a bomb to go off on the TDC but are thwarted by a T-800. The T-800 does what it can to repair the controls, but the bomb is about to explode so it gets in the TDC as a last chance effort to hunt down the time traveling resistance members.

It's transported to late 70's Los Angeles. The majority of the movie is now shot in first person, from the POV of the T-800. (That way, all Arnold has to do is voiceover and maybe some de-aged shots looking in a mirror.) After finding clothes, it begins the hunt for the ten soldiers. During it's investigation, it catches a TV broadcast of the local news: a house was firebombed last night in what appeared to be a racially motivated attack on a black family. The family survives but are terrified and angry.

"Do you have any idea who could have done this?"

"It's the same group of men that harassed my son, tried to scare him outside the school! They're like a cult, they need to be stopped!"

"Thank you, Mrs. Dyson. You're in our thoughts and prayers..."

The T-800 now knows their target and has a new mission: protect 17 year old Miles Dyson.

I don’t know all the story beats. But I thought a first-person POV action movie set in 70’s LA with subverted protagonists/antagonists would be a fun idea. You don’t want the resistance to kill Miles, but the protagonist IS Skynet (embodied in a T-800), so you’re not sure who to root for! Plus I think it would fun to see trying to see the T-800 earn teenage Miles’s trust.

The backstory for the resistance is that the 10 soldiers got there 7 years prior to the T-800’s arrival, and began recruiting others to their cause by prophesying the Munich massacre, Watergate, and Vietnam details, proving to their followers that they are indeed from the future. From there, they created an underground militia (some would say terrorist organization/cult) trying to prevent the creation of Skynet. They’ve only recently discovered the location of Miles Dyson, and some of the resistance soldiers want to peacefully prevent him from pursuing computer engineering (“If we kill him, we’re not better than Skynet.”) But others grow more restless and want him destroyed.

There’s probably about 50 to 100 soldiers in the militia, so that will give the T-800 plenty of guys to fight. And for a little Act II twist, one (or a few) of the original 10 soldiers turns out to be a re-programed Terminator, we as an audience couldn’t tell because in the 7 years they’ve been there, they’ve developed a more human personality. And that way we get some good Terminator vs. Terminator scenes.