I don't think that a throwing weaponskill is necessary. Players have been asking for this for years but honestly it seems quite random probably overpowered considering that there are already throwing weapons with DMG ratings of 250 in the game. I do think that a practical means to obtain shurikens would be nice though. Right now the best it gets is Koga Shurikens. They only come in small amounts from quests that nobody does anymore. Newer shurikens obtained via synergy would be fun.

Another improvement I would like to see is giving ninja the critical attack bonus trait. Innin and Iga back/body both enhance critical hit rate while Iga neck increases critical hit damage. Naturally I was expecting to see ninja receive this trait (along with other jobs like thief.) However, ninja ended up getting mostly useless traits like Tactical Parry, Magic Burst Bonus, and Skillchain Bonus. I found it quizzical that they got those instead of critical attack bonus.