SOUTHCOM needs 16 ships, according to its commander, General Kelly:
So as I said, I don't need a warship. I need a ship, something that floats, with a helicopter. … We think it takes 16 of those things to accomplish the 40-percent mission,” Kelly told reporters.
The Navy needs their high end ships elsewhere and needs the small hulls in the Persian Gulf. So nothing is left.
Something that floats and carries a helicopter is a low standard. Modularized auxiliary cruisers could do the job.