Horwath
Legend
It is an out-of-place technology in a world where people still use plate armour and shields.
But seriously, weapons in D&D aren't actually specific weapons — they are just sticks with numbers on the end. A rapier is "martial, one-handed, 1d8 piercing, finesse". You can call them whatever you want, since the names don't mean much (and are often misleading, like "scimitar" for "machete").
This.
my only beef is that arming sword(longsword in D&D terms) has the same damage.
if rapier is 1d8, then longsword should be 1d10. As you must pay with something ability to use dex in melee combat. And no, "versatile" trait is not worth equal to "finesse" trait.