The Boeing 200+ seater response in a nutshell
Boeing strategists believe they can impress upon the market the idea that one day a "Fattie" [2+3+2] might be incepted ... but any observer can see it's a mere sand-in-the-eyes Paper Tiger, for the simple reason that above a twin Y-class seat there's not sufficient space to install a proper hatrack. Therefore a "Fattie" (if any) is necessarily a [1+4+1], which btw is already in the pipeline : the staggered C919 ! Realistically, though, both A and B can produce cheap [1+3+1] sine die : H2XQR Series, H3XQR Series and/or H5XQR Series (which is the topic here) ... The [3+3] config extended beyond 37 rows is an airport ground turn-around nuisance and an in-flight service non-performer. I personally don't believe in A321 @ 236 seats, neither do I believe in A322 [3+3] ... the classical 757 suffered (as would your own 737 rewinged concept project) from the same disease ...