with the Aegis Air Defense System and the rail gun that is in development it would have a great future. If the Aegis air defense system is installed on Iowa class battleships it would be well defended against air attacks and with cruisers and destroyers being armed with the same air defense system i seriously doubt of all the ships that would be there supporting it, that one of them would not pick up a jet and carriers are still a much bigger target then battleships.
Unfortunately a battleship, even fitted with the Aegis combat system and SPY radar arrays is still very vulnerable to heavyweight torpedoes fired from submarines. The centerpiece vessel in a carrier battlegroup (the carrier) is protected from hostile subs by the escort screen which make up part of the CBG. These are ASW capable surface vessels, as well as usually 1-2 SSN's lurking about.
Even starting with a "clean sheet" for a new BB/BBG design, apart from perhaps fitting more guns and missiles onto a larger vessel, a BB/BBG would not have the flexibility which a carrier has in terms of operations, roles, etc.
Specifically discussing converting a old
Iowa-class BB into an updated design is essentially unworkable. The machinery, engines, power generation and distribution systems, etc would all need to be ripped out. What the
Iowa-class was fitted with is all out of production (in some cases, for decades). Also the class has been retired long enough so that many of the career naval personnel who would have been trained in how to operate and maintain the machinery are likely also retired, if not deceased. Even if some of the former crew are still in the USN, the chances that they remember what was required are minimal, since the most recent retirement for an
Iowa-class BB was twenty years ago.
As has been gone over repeatedly, high value naval vessels do not operate alone, they are too expensive and to valuable to risk in such a fashion. And the costs required to design and/or operate a vessel on the scope or scale of a WWII-sized BB are really only viable with the vessel in question has a great deal of capability. Something which is not the case if the major difference from smaller escorts is that a bigger gun and/or more missiles are the major differences.
-Cheers