Toby, when does Uncle Peter ever give you suggestions that don't take account of the stated requirements?
You should know better than to question my judgment.
You can fold one to five seats down flat, as you wish. You can fold the front three to act as a mini bulkhead, and removing any or all of them is another option, not a necessity. Should you wish, you can even move the blighters across as well!
Take the whole lot out, and you have a little van. In all seriousness, the entire seating system was the best, safest, and most versatile I've ever seen. Don't take that as a ringing endorsement of the vehicle Toby, the gearbox was notchy, the electrics could be temperamental, it drove like a
on snow and ice, and cost us a lot of money. It does however tick all the boxes you specified.