A321 has 8 door exits (4 same size as A320 + 4 smaller size doors, similar - but not the same as - A330-200 doors located after overwing).
Not that it changes the argument in any way on the crewing issue and required numbers (I agree with you 100%) but doesnt the 321 have 6 main door exits (same size as A320 - 2 foward, 2 middle and 2 aft?) with an additional 2 doors similar to, but not the same as, the A330 behind the wing? I may be mistaken but I took a 321 two years ago and I believe the second set of doors (where the second galley is) to be full operating (read - aerobridge dockable) doors. I could be wrong.
In any case, it shall be interesting to see what happens. As mentioned before, it really makes no sense to launch the 321 as the added passenger benefit (40 seats?) weighed against the crewing req and complication to the LCC, but stranger things have been known to happen. Given the separation of two cabins on the 321 by a galley, perhaps a domestic StarClass is on the horizon given DJ's premium Y announcement?
All hypothetical, of course.