You can buy steel crash tested seats, like Flexsteel, that can easily be nicer than your favorite chair at home, that are installed in RVs and/or custom vans. They can be mounted in various ways to be crash worthy compliant, bolted to the floor or frames.As I mentioned then, if I could find a class C with a crew-cab instead of a 2 seater, that'd be a no-brainer for me. There's no world in which I'm putting my kids at the dinette while driving down the road, even if a crash is unlikely. Those are not accident rated seats.
Any seat or couch in any Class A-B or C is removable, just remove and replace. Many RVs have enough space behind the driver's and passenger's seat to mount 2 more seats.
It is a no brainer!