Yes but how are you so sure no one would use them? I absolutely would use the HMS Mordaunt because I hands down like the way the ship looks. I mean lets face some facts here, in a game like this, player skill plays just as much if not a more important role in the performance of a ship, than the ship itself does. Also we aren't talking huge differences in performance, I mean perhaps a more modern ship is a few knots quicker or turns a few degrees faster or maybe can get a few degrees closer to the wind, but this isn't an overwhelming disadvantage that skill can't make up for so these older ships can still be effective. I any case, I can almost guarantee you that once open world hits, I will be choosing my ship as much for how it looks as I will for how it handles or what guns it carries because part of the fun is envisioning yourself on the deck of that beautiful ship your sailing around.
Anyway, I do agree that the devs shouldn't be wasting resources modeling ships no one will play but I would hazard to bet that quite a few of the earlier ships will be very popular and used quite often by those of us like me who aren't min/max types. Perhaps they should take some of the more popular older ships like the HMS Mordaunt to the polls and ask the community what they think and bring in a few of the more popular ones just to add a bit of flavor. Also, I think most would agree that there are quite a few newer, more modern designs that have yet to make it in the game that should take priory so while I wouldn't mind seeing some of the older ones eventually, there are probably about a dozen or more newer designs that make much more sense in the short term.