it could be done. if you put hinges on the bottom of the top half of the seat and cut off the metal hooks on the top part of the seat the if would fold. then you ould have to get a latch/lock type deal for the top of it.
about the little passthru. i think you could take off the silver metal panel. it would prob widen te opening some, i dont know how much bigger. its not necessarily the size of the opening tho, cause right now you have a big foam wall blocking the sound. i think it would be a ton louder cause i was ridin around with my backseat out the other day and my exhaust sounded a ton louder