Not much. Amon's psychic bloodbending already is as overpowered as it gets, as he can fold everyone into a cube and knock them out. He mastered his bloodbending to such an absurd extend, that he is even capable of blocking your bending, and the authors further noted that his bloodbending allowed Amon to sense his opponents attempts of attacking and interfering. Outside of bending, Amon already is a capable fighter. So, mastering additional "fighting techniques" and weapons wouldn't add anything to the equation.

@@vastvision3330yes but it would have been infinitely much more versatile in his fights and also it would have been too powerful and also unsurpassable and also unstoppable and also unbeatable and also invincibles if he had learned to master all that without exception