Yeah, even that is tricky. Every different manufacturer has different packaging for the cells. The Nissan Leaf for example uses a pouch style cell rather than 1

Yeah, even that is tricky. Every different manufacturer has different packaging for the cells. The Nissan Leaf for example uses a pouch style cell rather than 18650 cells. Even if you stick to say Tesla batteries you have to undo the wire bonding and probably spot weld each battery back together, then balance and charge the pack ensuring you don't have any duff cells. It's a lot of work for reclaiming batteries on an industrial scale.