I've been toying with this idea I've had in terms of weapon skills. Lemme know what you guys think:
When a character levels up, they're given skill points to allocate towards their weapon/s of choice. When they reach certain weapon skill levels, they can learn attacks of their choice from his/her weapon's level group.
However, if someone is trying to master a magic-based weapon like the Staff, not only are they given a choice to select a weapon skill from their level group, but they are also given sub-points that they can spend on additional spells.