1. Yeah, Jim/Harry has pointed out the WC flaws from day one, obviously, so the build up has to be the complete dissolution/re-organization of the WC. There will be a fight for that. Harry has been compared/related to the Original Merlin more than once. We know that only the original was the only other Wizard entrusted with the swords, and we also know that Harry is a direct line descendant of the original from Eb's diaries. That said, can you really see Harry as leading the new WC?... Imo, he would at most be a symbolic figure head for trail blazing the new era...
2. Mab, imo, is not evil. Think about what we know of winter. She is cold and calculating. She has definitely killed innocents, but it has been a calculus. Why? Because in this age it is Winter that is the guardian of mortal existence. She keeps the walls guarded, and the enemy at bay. Since she was once mortal she has the basis/foundation for Love/Compassion, and after millennia she is now a battle hardened General who has seen more loss than any one can really comprehend. Hence, cold and calculating. Each loss of life is a calculated balance while she fends off the enemy.
I can see him setting it up, but he isn't a ruler so I doubt he would rule it for very long even if he was "forced" to. In some ways, if magic were exposed altogether it might not necessitate a White Council organization per se. Harry is very anti-big gov/corp etc. I doubt he would every sign on for anything too centralized, in theory. Always harder to figure in practice.
Depends on your definition of evil I suppose. But most people tend to think killers, whatever their reasons, are pretty bad. Mab is far, far worse than that. She tortures people for fun and would kill humanity if she thought it necessary. Some might call that pretty evil. However, she is trying to do the right thing for Reality. So that's something. I think Jim's various discussions in interviews and AMAs etc have covered how his universe views it i.e. it's less about intentions and more about results. Mab might be intending to do the "right thing". Doesn't make it so if it causes more harm than it's worth.
A great example is Watchmen. If Mab had watched, she likely would have agreed with plan. I won't spoil it for those who might not know the movie but essentially the choice comes down to killing millions to save billions
. I suspect Mab would agree with that logic. But as Dan/Night Owl 2 basically says: you've saved humanity by mutilating it. It's not a black and white thing, in the real world. People tend to sit on different sides and there are many, many philosophies about these issues. Depending on what beliefs and values you may subscribe to that tends to influence that. As for Jim's Dresdenverse, there is actual Right and Wrong (per a WOJ) and whatever you're beliefs the universe still will pay you back for how much Right and Wrong you do. So I think Mab, and Harry, might get their just desserts. Even if they do save everyone...