Honestly, the goblin was extremely vague when it came to doing affixing materia. All he stated when it came to specifics was that it enhanced the weapon's capabilities. Could be a keener edge, could be something lighter than usual (that has its ups and downs), or other things.
If you wanted something more durable, you can find someone skilled in their craft, since we can technically increase the durability through the repair action.
Personally, I'd just call it as you stated it, a favored weapon. A favored weapon will bring some advantages to a character due to how close they are to it in a sense, mostly through skill and technique when wielding that particular item. That's how I'd play it out though.
If you wanted something more durable, you can find someone skilled in their craft, since we can technically increase the durability through the repair action.
Personally, I'd just call it as you stated it, a favored weapon. A favored weapon will bring some advantages to a character due to how close they are to it in a sense, mostly through skill and technique when wielding that particular item. That's how I'd play it out though.
