aux engines: fair enough, if engines are well protected these can be left out
propeller shaft: they make the difference from a lucky hit to the rudder sending your bb to nowhere and keeping it in the fight, at least the first step seems beneficial
barbette: fair enough except if you use super heavy shells with charges with high flash fire chances, I or II can make the difference between a loss and a destroyed turret
reinforced bulkheads: fair enough, but they are useful if you go for a 0 extended belt/deck armor to keep large caliber fore/aft hits to propagate inside
anti flooding: same as bulkheads, they can be skipped unless you go for a true all-or-nothing, but I rarely go over anti-flooding I, compensating with tower with high repair bonuses
citadel: they can convert efficiently weight to cost, no much use otherwise, albeit either a citadel or a aux engine to preserve mobility can be nice
shell weight: fair enough
turret traverse: fair enough