To be real clear on this; you cannot evolve or upgrade Traits. Existing Traits could be complimented with subsequently acquired ones but that would require a case-by-case assessment of the abilities you want.
Like, I would not allow a Trait that is like "Aura of Fear gets a further +10 and inflicts Frighten now," If you wanted to compliment it you would need to have something that plays into the effects of the existing mechanic.
See above, it would really depend on what you want to do.Though really, that one's pretty good as is, but I'm thinking something like it being a thing corresponding to the Mind Effect of Disinterest the way this one is corresponding to the Mind Effect of Fear, which I would then potentially upgraded to correspond with the Mind Effect at the next level which just gives a Surprise Attack as the enemy Loses sight of Jane lol
Which is just kind of a different way of doing the trait/technique combo you mentioned with the Stealth thing you have in your example section really.