Phalanx at B position was trialed on one of the T42 B3’s, HMS Edinburgh and it was found to be unsatisfactory.

Interesting. Your explanation (and wiki’s) is not the one I heard but that don’t mean that I’m right and you’re wrong.

Also, do the T42’s have the weight margin to have both Exocet and Sea Wolf while not turning turtle.? Plus the space for the optical trackers and

computers.

Quite possibly not. And in retrospect (or in fact upon reading your post) this is blindingly obvious. Putting all of the extra weight on one section and a high up is a bit daft.

So:
Keep lightweight seawolf amidships and fir Exocet in ‘B’
Keep Exocet on hangar and fit Phalanx amidhsip
Keep Exocet on hangar and fit VLS seawold in ‘B’
Invent magic SeaDart launcher capable of handling Exocet and fir lightweight seawolf amidships
?

Decisions, decisions

The B1 and B2’s also had a narrower beam (14.3 versus 14.9) so they might not have the stability to have their length increased.

Now that one is easy. Weld a second hull around the first. More beam, more bouyancy and twin hull vs. icebergs and torpedos.