If some char do some thing very often, he could get trait related to that thing. For example, if someone is practicing spells a lot of time, he could get trait which will give him +1 int and +20 mana. Traits do not have to be positive. Sitting in the guild while he practices spells could give him trait 'ill health', for example -1 str -10 hp.
This sounds pretty neat, but I think maybe it would be best as an enhancement of limited duration, or for as long as whatever it is that enhances the trait continues. So, how natures grace only continues for as long as the character is in woods, these could be similar.
So for example, the additional moves trait (from lots of walking) only continues as long as the char keeps the walking going. Once they stop and do something else, maybe it goes away. And as long as the char sits in guild practicing spells, the +1 int stays, and then if they venture out and walk around, after a while the +1 int goes away.
I think that could be interesting too!