I originally posted this question in /r/Warships and didn't get a response so I'm posting it here: If I remember correctly, I've read that the US Navy planned to keep many of its Super Dreadnaughts into the 1950's, only replacing them as the battleships ordered in the late 1930's and early 1940's came into service. I've also never read anything about plans to rebuild these old ships before they retired.
My question revolves around the attack on Pearl Harbor and the rebuilding of many of these ships. Some were so rebuild that the December 6, 1941, battleship would be unrecognizable next to the ship as it was on VJ-Day. Were these rebuilds done using preexisting plans or were they kind of done on the fly? And if the redesigns were done in a very short amount of time, what limitations did some of these ships have?
Just to clarify what you are asking, are you specifically referring to repairing/rebuilding damage that was caused by the Pearl Harbor raid, or are you talking about general modifications/upgrades during the entire war?
Of the battleships that were sunk/damaged during the Pearl Harbor attack, two were not returned to service. The Arizona was pretty much completely destroyed, and while the Oklahoma was raised, it was decommissioned in 1944 without seeing much in the way of major repairs. The West Virginia and California were sunk and extensively damaged, and after substantial repairs returned to service in 1944. Finally, the Nevada was beached to avoid sinking, and was able to return to service earlier, in early 1943.
Like you say, these repaired vessels were very different when they entered service late in the war than they were when they were sunk, but that's also true for pretty much every capital ship in every navy during the war. Vessels frequently went in for refits and modernization as the war developed, in the US, British, and Japanese navies. Most of these refits had to do with weapon layouts, radar, and fire control equipment; as technology progressed, and aircraft were demonstrated to be more and more important, there was a general trend in most navies to stuff extra AA weapons wherever possible, and improve the methods of aiming those weapons. As the above Pearl Harbor vessels were under repair, it made perfect sense to refit them to a modern standard along with the rest of the navy by the time they entered service.