Neat concept, but perhaps less crafting-oriented and more "effect"-oriented. Maybe going through a quest chain to unlock runes (make them relevant to the game) and then have you do some kind of challenge to collect them, maybe with particular specific challenges that don't amount to "Kill X number of Y".
The effects of runes don't need to be "X of Y stat" as in D2. That was a huge failure in part because the only use of runes was then the specific items. Rather, maybe adding skill effects like "Your Super Arrow now deals splash damage" or "Whirlwind now coats enemies in tar, leaving them more susceptible to fire damage and lowering their movement speed".
Gogok + Mirinae + Pain Enhancer would be my choice
While the buid is a little past its best time I still liked the gameplay (shields.. shields everywhere!). IAS is strong stat there thus the choices. Gogok would bring benefit to Law and other cooldowns along with obvious IAS boost. Pain Enchancer is strong for any IAS build and Mirinae is no brainer imo.