You're giving up the sources of damage in the game (TWF/THF). Therefore, you need some real bonus damage. Maybe Dex to damage as a start. In addition to Precise Strike, with better advancement. Maybe give it an extra attack at the highest attack bonus or so, and some Critical-improving abilities. Also, removing the cap on the Int mod to AC would be a good plan. And yeah, lower prerequisites would be nice. And allowing light armor.