“They will only pay for aftermarket parts, not new.”
Aftermarket parts are not used parts, they are new parts. They just aren’t manufactured by Toyota.
It’s just the back end of the car. Once they fix it, what are you afraid will have cronic problems?
Get it fixed and keep driving it. Bemis has a good point, try to get NEW battery packs out of the deal. Have you ever priced out how much it will cost you to replace those battery packs?