Everyone join the BBBB (Big Beautiful Battleships)Club. Not only would their existence mar a shift in Starfleet thinking away from the canon one ship fills all multirole approach. But Battleships do not need engineering/Science compartments so we can stuff as much gun as fits into its frame.
Also who does want to see the sheer beauty of a big Battleship smashing Romulan warbirds with big cannons?
I do and so should you.
So the thing is, single-role ships only make sense now, but will fall out of ROI eventually. High guard (read:space coast guard) ships sure should be onerole. Cheap and efficient are the names of the games, they don't even need warp drives. But pure battleships don't have such a role and will increasingly be mothballed and eventually scrapped.
But having updated designs on file for wartime exigencies? Yeah. That does make sense.