well in my personal opinion there should be a classic and medieval era swordsman and the reminiscence era should be the terico and both the pikeman and the medieval era swordsman would upgrade into it i feel that it would be the most natural progression and the samurai were defiantly a medieval era thing so it would be rely weird for them to be a classic era unique
The thing is though is there was practically no evolution in metallurgy between the classical era and medieval era.
Romans could produce higher carbon steels and these were being smelted during the peak of the Empires wealth and this steel was just as good as any steel that could be found during the high-late middle ages.
However that wasn't the norm either in Roman times nor in the middle ages. The thing is that for most applications high carbon steels weren't necessary and the extra cost involved probably meant that the benefit was rarely worth it - they just didn't always bother forging high quality steel.
Roman legions may have had inferior quality of metal in their equipment but it didn't really matter. A low carbon sword is still lethal. Ultimately it was the organisation, training, economy, leadership that made them successful as was their policy to add defeated people into their armies. The quality of the weapon probably made very little difference to the outcome of a battle or war.
The Roman helmet though was one of the best mass produced helmets in military history - the amount of protection it offers, made it a magnificent piece of armor.
European Knights may have had better armor then the Romans did but you have to take into consideration the size of the armies here. The knights were the aristocrats - roman aristocracy on the otherhand considered themselves above warmongering and would spend their time talking philosophy or politics, bathing or whatever else the luxurious life in Rome offered.
Most European medieval kingdoms could rarely equip, pay, supply and field and army over 15,000 in size - and that was generally only temporarily - usually you are talking about < 0.5% of the population.
Rome on the other hand had armies deployed across a vast empire in the 100,000s - In the Punic wars Rome had 5% of Italy's population deployed.
Then during the peak of the empire consider the number of legions deployed from Britain, to Germany, to the Danube, to the Persian front etc...