The bit at the end is necessary to make it a happy ending; what's the alternative, everyone dies and a new one is defrosted? That would be a serious bummer ending.

And you know what, the AI is strong enough. Look at what the human does the entire time - he carries some canisters around, and drives out to look at a wrecked vehicle. (At least, I don't remember him doing anything more complex.) A really weak system can drive cars across the freaking Mojave desert! The canister stuff could be automated by a 8-bit microchip.

The clones are easily scrapped as a plot device. When the protagonist's shift is up, he climbs into the pod - and his memories are erased by an injection or something. He climbs out with total amnesia, is told the trip up damaged him and may have caused moderate memory loss or hallucinations, and sets to work at his new job... I think that's pretty sinister and creepy myself, possibly even better than the clones.