Originally Posted by
ty97
This is a key piece, IMO, to make this work. B needs to all one zone (whichever zone it may be).
B can remain zoned (though of course I would prefer it not to be) as long as the option of a secure non-Schengen transfer to Z and a secure immigration to B/A can be ensured. That, actually, would "only" require immigration passport control B>B, in the MVP form