My current plan is to do Worcester, MA, where I've been living these 30+ years, and include the entire central Massachusetts region. I'm sure that there will be some overlap with Boston, as well.
Of course, the White Council rep will be this wizardly investigator character that I've been working on in my head for the past, oh four or five years... a cross between Harry and the 10th Doctor, with a touch of Shaun Spencer and the Michael Westen (Psych and Burn Notice, respectively) voice-over. ("When you're a wizard...")
Of course, the way that I see him in his first story, he's more on the power level of Harry after the fifth or sixth book...
And some of his friends are also a bit high on the power level, but not without drawbacks.
My research into central Massachusetts folklore and such hasn't turned up too much, but I figured I'd be beefing up what's already there and creating a few other things...