A Brockton Bay without Coil is an interesting scenario to me, because it would so severely shift the power balance that the city would be utterly unrecognizable when compared to canon.
Because unlike how fanfic commonly depicts Coil, he is a known factor. His powers aren't. But Coil and his mercenaries are one of BB's 3 powerful gangs.
Take him out of the picture (let's say the asshole has a brain aneurysm) and the entire structure of the criminal world in Brockton would be radically different from canon.
For example, there's no Undersiders. Rachel would likely remain a solo villain, extremely distrustful of anyone and everyone, though she could end up in a team, maybe with Trainwreck since Wildbow does say that they'd have gotten along. Alec would've just kept drifting along, piecing together his own personal morality based on not wanting to be his dad. Brian'd still be an enforcer for whoever would hire him, trying in vain to save up enough to get custody of Aisha, though I could see him making a small team of his own. And Lisa probably keeps pickpocketing until somebody realizes her potential, hero or villain.
So many factors of canon would be completely non-existent without Coil (no Dinah kidnapping, no Trainwreck infiltrating the Merchants, no Chariot in the Wards, probably no Leviathan attack, so on) that the creation of an interesting AU just from that is a gold mine for a fic.
