For anyone who may try and scrap a rover, but find that you can't pick it up, you need to package it first before you can pick it up. Once you package it, set it close to the shredder and then unpack it. If it did not have a seat on it before you packet it, once you unpack it, you will find that it now has one, and you will then be able to pick up the damaged rover for placement into the shredder. Hope this helps.
I just finished taking the large rover out into the field with two RTG's on the front, two large batteries behind the seat, along with a medium storage module by the seat. Behind the rover, I pulled another rover with eight medium storage modules on it, followed by one more rover with the XL shredder on it, and two medium storage modules on the tail of it. I had eleven modules full of scrap, plus two on my back pack when I ran out of room on the modules. This is a scrappers paradise. You seem to never run out of damaged parts to shred.