The problem is not just the cost of the ships, but that the swapping was supposed to be quick, but right now it can take days or weeks, which is more like traditional refitting. But the model of modularity and being able to take on different roles is a good one. This is where adding in unmanned systems in the future will be an aid. If they can carry them onboard, whether it be drones to mine or sub-hunting underwater systems, all ships should be able to do such multiple roles simultaneously.