Stuffy.
The Airbus fuselage is wider. Really?
By how much. And who really cares. Have you ever been down the back of a P-8A? There are virtual tours available on line. To my eye, it looks like there is more than enough space for kit in this digital age. In fact, it looks as if there's almost too much space.
Your understanding of ASW, in the realm of MAD is astoundingly shallow, if you pardon the pun.