So since the Mage's guild is getting spell crafting for magic abilities, the Fighter's guild should get one for stamina abilities. Once you beat the Fighter's guild, you can choose to specialize your fighting abilities and create your own combat techniques.
Instead of searching for runes, you could take a weapon of your choice and be tasked with eliminating a tough creature placed somewhere in the world. Upon killing it, you would be required to meditate at a certain location to reflect upon your battle, such as on top of a waterfall. After meditating, you will acquire part of a skill relating to that weapon that can be combined to create custom abilities as more are gathered.
Thoughts?