It's true, the FBI agents aren't the sharpest characters in these stories. Presumably, they saw Chandra and Sonja as beneath their trouble, while they focus on more important work. But it's never good to underestimate any opponent.
I thought it would be a good idea to bring back as many main characters as possible for the epilogue (except Ashley, sorry - though you can bet she'll return

I understand your feelings about human trafficking characters. I think I was inspired by Dave Dorc's use of the device in his stories, but it's become more difficultto include as the tales get more complex and interconnected; I don't think I'll be returning to it (at least not to this extent).
I'm glad you still enjoy the humor, dialogue, pacing, and rhythm. I do my best to make the stories fun and smooth to read. I love developing these characters, and it's always great when some of them become more popular than I would have expected (like Carolyn and Atsuko).
I do understand your point about the complexity of the story, and I'm starting to agree. There were still a few too many characters in this saga, and it was a struggle at times to incorporate them all. I'm actually planning to do a short spinoff story (or maybe two) focused on some of the side characters before giving the larger Volume 5 over to Bridget and friends (plus Chen and enemies).
By my count, a lot of the criminals (Karima and most of her crew except Sabira and Zuhal, Farah, the Bombshelles, Valencia, Lucille, Melissa, presumably Maxine) have been caught, and most of them will likely not return. I do like having some villains escape (or talk about escaping, as they are wont to do) as I enjoy writing them, but I try not to let all of them get free. Gotta prove that crime doesn't pay (unless the crime is mugging other women for their uniforms, of course). The ones who do escape will probably have a role to play in a future story.On a side note, I'm starting to notice a pattern of all the main criminals seemingly being able to easily escape the authorities, which I think could become a hindrance in the long run, as it risks to desensitize readers when it comes to the stakes of the story. The idea is that if the bad guys can never truly be stopped, readers may start to stop caring about the stakes of the story since the heroes seemingly never truly win.
I have something like this in mind for Volume 5. It will hopefully be more focused than Volume 4. I will try not to make it overly complicated, though sometimes I just can't help myself.The story seems to be gearing to the gathering of a 'League of Villains' to try to bring down Bridget and her friends during the next (last?) installment of these series, and honestly I'm impatient to read about it. I also think that having the characters form bigger teams could be a good way to keep a high number of characters while reducing the number of competing storylines: by having groups of numerous characters having at least one similar goal: for instance, a team of 'heroines' around Bridget, one of 'villainesses' around Chen, and the FBI as the 'wild card third party'.

First, there will probably be at least one short story (focused on some of the secondary characters, and resolving some of their storylines). Hopefully the greater focus makes for a smoother reading process.
Thanks again for your thoughts, and there will be more to come!
