I like the idea of a character who really doesn't have a lot of raw power to use in the field--maybe a basic shield or a basic attack, but nothing more powerful than bulletproof glass or a handgun would be--whose real strength lies in crafting objects. Dresden has a few enchanted items that help him out, but of course he also has raw power, enough of it that his crafting really only has to serve as a channel for his power. If your character is like a magical version of a techie, that could be quite interesting.

What I've noticed about Dresdenverse magic is that its efficacy is often quite dependent on what you're targeting with it, thus the knowledge-is-power aspect. Knowing your enemy is basically required for defeating them. Your character would have to know the canons inside and out if she wanted to create enchanted objects that will help her defeat the Sues. Magic probably changes depending on where you are, too. If it can be different depending on your Dresdenverse location (i.e., ley lines), and different depending on the culture where it's used (the walking techbane effect is largely a modern phenomenon)... then it can certainly be different depending on which continuum you're in.

Yes. Sues are soulless, and the first law doesn't protect them, no matter how human they look, any more than it would protect a White Court vampire. But say your agent kills a human anyway; how would the Council track them down? It's unlikely that the Council knows about the PPC. On the other hand, your agent would probably know better than to attract their attention to her activities, because the Council (or anyone in Dresdenverse) knowing about the PPC would be asking for trouble.

Soulgazes, by the way. Avoid them. If your wizard agent ever looks anyone in the eye, they get to know that other person, and the other person knows them, in great detail. And that detail can't be forgotten. Neuralyzers would be useless. If she ever ends up exchanging a soulgaze with a canon, she's automatically given that character unerasable knowledge of the PPC.

Regarding minis: I don't think Mouse is a good Dresdenverse mini because Mouse isn't an antagonist, or a monster; he's just a big dog with Spidey Sense and unusual intelligence. We already have Sparklewolves and Puppies of Baskerville, so keeping the dog-type minis down would be a good thing.

I don't really have a good idea for the mini, but some possibilities:
-Demons. Come in multiple types, shapes, etc., which can be varied according to which name got misspelled.
-Skinwalkers. Creepy, yes--but it's Balrog-level powerful and definitely a monstrous villain. Its shapechanging power might make for good comedy.
-Fey creatures--maybe Gruffs, or various members of the Wild Hunt.
-Ghosts. Not quite villains, but they are echoes created by violent deaths. Maybe they could be created by plot holes, too; if Harry Dresden can create his own ghost via almost-a-plot-hole resuscitation...

Anyway, if you find the first Dresdenverse mini, it's really up to you, but I really think you should get creative; Mouse is wonderful, I love Mouse, we all love Mouse, but another dog mini would be a bit repetitive.