I understand where you’re coming from. The design wouldn’t take a long time if the USN could write a simple specfication and put it out there to the shipbuilders. If they take a proven hull & engineering, you cut out all the modeling and testing. Remove the Aegis system, put in a point-defense AA system and retain the Sonar Suite. There’s your interim design. Start building this year.
They you build a cheaper design on a new hull. Single screw, gas turbine. Or you take the Coast Guard’s new endurance cutter and muscle it up a bit.
Yeah, those could work. Especially since they have a small 115 man crew that is about the same size as the Littoral Warfare vessels. If the navy were to give them a 75mm or 115mm cannon rather than the 57mm along with a a small 12 tube VLTS that could carry some combo of Harpoon, SM2 and ASROC. Then add a CWIS and improved sonar and radar. They don't have the stealth of some of the newer designs but I bet they could be built for less than 700 million each even after up gunning them; especially when you consider there would be almost no development cost. They'd be sort the opposite of the Littoral Warfare ships which are really fast at 40+ knots but evidently rather flimsy while these would be a slower at 28 - 30 knots but with much more firepower. I bet the cutter design is more sea worthy and has better sea keeping abilities too, especially in heavy seas. At 4500 tons displacement they would be a big frigate and could be considered either a large frigate or a small destroyer. There is sort of a rule in naval design; "Never build a replacement class of ships that is less capable than the ones it is replacing" The navy sort of broke a rule with the Littoral Ships, Their only real advantage is speed.