Following that logic, we would only need a fleet of 20-30 really capable ships.
But we'd never have one where it was needed.
The LCS size and concept is the right one. We could go even smaller.
But we need at least 100 more ships and 40-50 more subs over the next 10 years.
Beyond just replacement.
I think that the USN should get proper frigates (something in the same ballpark as the German F125 frigates) rather than trying to up gun the LCS.
Historically the best force projection ship has been the cruiser. Go anywhere, show the flag, use gun boat diplomacy. If the Navy used a 18,000 ton platform it could perhaps avoid the more costly stuff.