Scavenger

I like the idea of getting a cosmetric extra once a skill category is mastered. So you can a bit roleplay into your role 😀 Edit: At the other hand there shouldnt be something which "force" you to get every skill maxed of one category since some skills within a category dont make sense to max. depending on your role)

Was thinking about how mining in its current state could get some more depth. What about a "Timing-Minigame" which needs you to release the mouse button (or click a second time) when the mining sphere reached its max size (Maybe a tiny threshold). Once you timed good you get a buff which lasts like 3 seconds and will give your next mining sphere in its first second of growing a tiny boost like 10%. A tiny start boost of growth could already feel satisfying and make you feel you are in the flow That minigame could be indicated by i circular loading bar which makes a satisfing "blink" in its neutral white color when you timed good. But it should not appear red if you dont since the player shouldnt be punished if he doesnt care about it.