Wow, I think this is difficult to evaluate. Generally, I would say not playable. You pay 4 mana and get a 4/2, a 3/2 or a 5/2. Of course, Pirate Warrior can build up their weapon, but since they also want to hit something with it (Face or minions), Phantom Freebooter will usually have very low health. so maybe a 7/2 or even a 8/2? It usually will die.
And there is no value in keeping the weapon until it is very big, because of the danger of weapon removal. And I presently do not see another deck than pirate warrior that will build huge weapons.
Another Card I completely misread. 3/3 plus weapons stats. That is more appealing. I don't know whether that will be enough, but with a 3/2 weapon it is a 6/5 for 4. That is okay and probably better than Naga corsair.