Roman armors in the medieval? no thanks
You know Caldaria is a fake world, right?
Plus we have guys playing in armour ranging from 4 th century all the way up to the 16th century. These armours would never be seen together on the same battlefield anyway. So any argument "to maintain historical accuracy" is shot to pieces before it even takes off. Not to mention that guys mix and match armour sets on the same chars not only from different centuries but also from vastly different regions as well. So lets add these armours into our fake little world, they are super cool from two of the most interesting civilizations ever and they look great, what's not to like.
P.S The Roman Lorica Segmentata was used till the 4th century by mercenary troops, so even if you are going to go down the "historical accuracy" route, Roman armour should still make it into the game, as it was used in the early medieval period.