Ever see a half-orc welding a rapier? I didn’t think so, but a half-orc thief would have to. Let’s fix that.
Finesse Master
Choose one weapon. You are now proficient in this weapon, and this weapon now count as finesse weapons for you.
Thoughts? Does this need to add to your dex? It it too powerful as it stands now?
Throat Punch Games 
Thought this was already available..?
You can gain proficiency with a weapon, but you can’t make a weapon a finesse weapon. Think great sword rogue. This does both. I don’t think it over powered as feats a really powerful in DnD 5e.
You have a valid point but in order for a weapon to be finesse it would need to be light and easily handled. Finesse is not a physical ability but a function of the weapon itself. You would just have to up their strength to make any weapon a finesse weapon or there is a feat, I think, that does something similar.