I don't really think that's it, Harry is clearly getting set up for a moral conflict, a clash between who he wants to be and what he thinks he needs to give up to do what he sees as necessary. And I think Butcher has done a better job than most to make the fatal mistakes more plausible than simple hubris or bad judgment or a lust for power thinly disguised as altruism. What this book hammered home more than the others was how Harry is being perceived as evil or in danger of it. Even more than Mab's proposal, we see him having a much more amicable and convivial relationship with Lara in this pair of books, when it's been made abundantly clear in prior ones just how much of a villain she is. It seems almost like she's being made nicer in this, such as her abandoning her ruthlessness to pursue Thomas' well-being no matter what, and finding common ground with Harry through that.

Except Thomas really does have it coming. Justice does dictate that he be punished for the life he took and the one he tried to take. Yes, Justine's life and their unborn child were threatened, but is her life more important than Austri's? What about to Austri's children? And Thomas was not being possessed or controlled, he made his own choice of his own free will. It's certainly understandable, but it's still not right. He basically sold out reality by going along with Nemesis' demands, which is particularly egregious for a Venator. Lara's & Harry's side mission, which they plot and execute so effectively & chummily, is basically thwarting justice by helping a guilty fugitive escape punishment. They were endangering the Accords, which are a critical defense of existence against the Outsiders (I mean, why else would Mab give a shit if ghouls and vampires and wizards got along with each other, unless she intends to have them available to help when the Outsiders make their push), and doing so in accordance with the plans of He Who Walks Beside.

Harry crossed the line without knowing or acknowledging it. He's not being misunderstood by Ramirez because he can't tell him everything, that's just covering for the fact that Ramirez would probably legitimately disagree with his actions, even if he could sympathize with Harry's desire to save his brother. Who, like Harry, has been in the trenches beside Carlos before this.

So while Harry's rightfully worried about temptations and what he sees as the necessity to save people impelling him to compromise himself (which is consistent - recall the debate with his subconscious about accepting Lashiel's help against the necromancers in Dead Beat. His primal impulses, not his rational faculties or conscience, called him a coward for refusing demonic aid, and claimed that anyone who died because he would not turn to the Dark Side to get the power to save them would be his fault. So that's a fundamental position for Harry), he's probably slipped further than he realizes, and all those people giving him the side eye and being afraid of him, are not misjudging as much as we know.

So I think Harry's going to have to steer out of this skid. It's not going to be as black and white as rejecting Lashiel's coin in the Raith Deeps. He's going to have to undergo some serious growth on this one in order to get to a place where he can accept that people get killed and turning himself into a monster to stop that is not really helping.

I kind of like the idea, but I think it would serve more as an illustration for the readers, rather than a wake-up for Harry. I think this possible "good Harry" might be lacking in other ways. A recurring idea in the books is how suffering builds character, and how Harry's constant beat downs and struggles have fortified him mentally and spiritually. I think an alternate "good Harry" would be more likely to be hollow, like the World without a Dark One that Rand saw at Tarmon Gaidon. I think the superficial takeaway from meeting alternate good Harry is that our roughed up, creepy, flirting with darkness Harry is the better one, even if Harry is going to be troubled by it, while on another level, good but wrong Harry will have some vital point that OTL Harry misses, albeit one he can work on in the future, because he has the character and strength to do so, while good alt Harry would probably fold like a card table when the going gets tough.