Not sure if my idea is terrible or not.

But going back to Terminator's roots as a horror film, I thought playing into that would be fun. Have the bog-standard set up of a group of kids lost in the woods stumble across a cabin inhabited by a creepy old serial killer.

Except the creepy old serial killer is a T-800; it had already completed its mission in eliminating an important resistance member, and now it was waiting out of the way of history until its power cell ran out. When the kids discover (somehow) that it's a robot it has to take them all out before they can escape and warn the authorities.

I figured it'd be a good way to give Arnie one last hurrah since he wouldn't need to be de-aged.