Artificial limitations add no value to the game, in my opinion.
There are no artificial limitations. Ships did not appear out of thin air in the 15th century in all sizes and variations that hundreds of years of experience and learning about sailing have produced.
Each of them is the successor of an earlier ship that had limitations or drawbacks that were eliminated, e.g. by new inventions or larger shipyards or more experience how to sail with or cruise against the wind and using a modified takelage.
Having them all available at the very start of the game would beg the question why Columbus did not ship from Spain to Hispaniola in a comfortable and safer ship that historically only existed centuries after his death.
But West Indiaman doesn't compete with a single Caravel, now does it? 3x Caravels can deliver the same amount of cargo as upgraded West Indiaman - and they absolutely have more chances to survive a pirate ambush. Although, Caravel being by far the worst ship in the game, it loses comparison to anything.
Caravels are the best ships in the game - because when Columbus set sail they were the most modern and only ships available that were halfway suited to sail across the Atlantic (as compared to the sluggish ships the Hanse used in the Baltic or the oar galleys used in the Mediterrenean that had to stick to calmer waters and navigated mostly in sight of land).
Every other ship model came later.