I wonder why they chose Phalanx instead of Goalkeeper? Topweight / Space / Deck penetration issues?
Reckon you're right with the space/deck penetration issues...relatively speaking, you can plonk a Phalanx almost anywhere on deck it'll physically fit and have a clear view from. Goalkeeper is a much heavier system which requires significantly more under-deck space (its ammo is stored and loaded from below, whilst phalanx has a drum mounted on the gun itself).
Goalkeeper also costs a lot more
.....but seems to me the better solution, though if it just won't fit, then it just won't fit.....