Nissan isn't buying back a CPO truck that they have a factory approved repair for. Not happening.
I really don't understand why so many people, including the OP, just aren't getting that, at all.
The OP didn't buy the truck new from Nissan.
He doesn't get the same types of protections that a new car buyer would get in this situation.
He bought a used truck. From the dealer.
Certified Pre Owned means its a used vehicle.
There's no Lemon Law here that can be used to leverage the manufacturer.
There is no contract between the OP and Nissan, just with the dealer.
Honestly, getting the frame replaced is a perfectly fine resolution to the whole situation, and I don't understand why anyone who has ever owned a pickup before would even bat an eye at this repair. They are going to replace any wiring harness fasteners that are damaged during removal. They might find things that were rushed during original assembly to repair.
But, there's no point looking at Nissan and expecting them to give you a new vehicle in replacement for a used vehicle you bought from one of their many dealers. Nissan is meeting the requirements of their 3 year 36k mile warranty with flying colors. Didn't even bat an eye at the need to replace the frame.
OP is better off waiting for the vehicle to be repaired, and handed back to him, so he can then take it to a shop to do a VERY THOROUGH inspection, and then he can use anything they find to go back to the dealer and say that this that and the other needs to be fixed. After all issues are resolved, he can then drive it, sell it, or set it on fire and collect the insurance money.
But no one is giving him a new car or truck until he goes into a dealer and buys one first.