Since the last time I called to the universe and the universe actually answered, I'm going to try again.
You know what I want? After "Burke's Seven," I really want that AU where Peter is the head of a crew. In another words, I want a Leverage AU of White Collar. Peter would make an excellent Nate, without the alcoholism and asshattery. The thing is, in my head, it'd take something pretty significant to turn Peter away from the law. It has to be a situation where the law failed him utterly and broke his faith in it. I don't think it would necessarily change his character in a fundamental manner. It would be an extension of his character. Peter isn't so much law-abiding as he is ethical. It's justice and morality. It's just he seeks the expression of it through rules and law, which makes a lot of sense, considering he's a math guy. Every equation must have a solution. Even insolvable equations imply that there is a solution to be discovered. There is an inherent structure and sequence in everything.
So I would find it really interesting to see how he would regain/adjust his worldview should it be turned upside down, when law is no longer the means through which he can find justice. The problem is that I think the biggest thing would be if something happened to Elizabeth, and that'd be pretty cliched. I don't want to do something to a woman to create a change in a man. Like that doesn't happen enough already. I don't think something happening to Peter himself is enough to inspire a change of that order, but the show hasn't set up anybody else important enough in Peter's life, other than Neal of course, but Neal can only be the trigger if we're splitting off during canon time. Which isn't necessarily not what I want, because I'm not sure when I'd want the trigger to be, whether Peter deviated into this life before he ever joined the FBI, or some time before the show began (before or after Neal became a case), or during canon.
Furthermore though, I'm not sure what the trigger should BE anyway, because it's not enough for it to be a miscarriage of justice via misapplication of the law. Because Peter is fully aware that human beings are corruptible and fallible. It's not enough if a crime to a loved one is unsolved due to incompetence or corruption. It has to be some major systemic problem. A giant "the system failed me, and failed me COMPLETELY" situation. Nate's case on Leverage functioned as a personal misfortune (death of his son) caused by systemic shenanigans (blanket denial of all coverage claims) expressed through one greedy asshole (Blackpoole). I think you similarly have to tick all three categories to push Peter over that same kind of edge. But you might need even more, because Peter is firmly Lawful Good, to steal a term from D&D, whereas Nate has always been morally ambiguous (not sure where he'd land for D&D alignment).
The most likely situation would actually have to be in canon, I think. Where something happens to Neal on a legal front, so Neal suffers suitably in a manner he does not deserve, all because of the law, but Peter will have to be burned out of the FBI to really get that edge going, too. With that said though, Peter is a character who strives for stability. I think it was
the_grynne who said that despite the fluff of the show, Neal is not a character who could ever settle down, and I agree. Conversely, Peter is not a character who can go on the lam forever either. Peter and Neal are ultimately a Venn diagram, and this probation period is where the twain has met, but otherwise they occupy completely different worlds. Which isn't to say some form of compromise isn't possible, just that it'd be difficult to come up with a resolution that would satisfy both character and situation.
The more I talk about it, the more I want to write it, but I don't even know where to start, because I have no answer to any of the questions, not to mention that I don't seem to write anymore. Besides, I'm lazy. I want somebody to write a delicious epic, and I can hunker down for a good read.
SO, I BESEECH THE INTERNET: SOMEBODY WRITE THIS FOR ME PLS. MAKE IT GOOD.