The issue I'm having with A Fistful of Divas is this:
A good comedy will have some pathos behind it. A little weight. In Have Gun, Will Play, Mick and Casey may be innocent and wide-eyed about civilization and luxuries like toys and silk drawers - but they're also paid killers. They are very much aware that they are on the outside of society, looking in. Early in the story Mick and Casey witness the shooting down of a harmless old man, and they get into a shoot out with the perpetrators. Since Casey - who is still just a teen - grew up with that sort of violence all around her, she's angry and though she would never admit it, she feels helpless. Late that evening, she reveals a little vulnerability to Mick in the middle of an argument as to whether they should go chasing after the killers.
“Every place is like this, ain’t it,” she said, her voice so quiet I could hardly hear. “Every place.”
“No it ain’t,” I said.
“Every place we go. Outlaws shooting and messing things up....”
“Some places are like this. Not all of them,” I said. “We just keep moving around and running into it. It’s our job.”
She nodded, and looked in her glass. The fire threw flickers of light across her face, which looked red, but she wasn’t crying.
“Like dirt,” she said, lifting her chin. “It gathers and we clean it up.”
Both of them are treated like saddle tramps and bums by the rest of the world, and they both struggle with their value to the universe. You could say that's their life long quest, to find the meaning of what they do and who they are. It's the theme of the series. (And of course, Mick WILL solve the murder of the old man, though it will seem lost in the sweep of greater events for a while.)
But those kind of contemplative and thematic elements really work better in a novel than a short story - especially a light mystery puzzler. You might have touches of it in a short story - just personality quirks. In "The Hoosegow Strangler," the very first Mick and Casey story, they have to worry about taking the blame when a witness they're guarding is murdered. It's always a struggle for a good-natured young doofus and a teen-aged girl to be taken seriously as gunslingers. But he is smart, and she is tough. And that contrast is a part of the comedy.
My problem for A Fistful of Divas is that it started as a short story, and then a short film script. In both cases, the theme stayed on a frivolous level. As I sit down to thread in more complications to the story, I realized quickly that this story needed more weight.
Last night I played with one thread that looked fruitful. Mick and Casey have long been on a quest to hear an opera, because Casey's father had bemoaned the fact that she'd never hear one if she married Mick. And in this story, they get the chance, except that an attempted murder thwarts the concert. And Mick lets Casey down at a key moment, and feels doubly obligated to solve the crime and get that concert back on track as a gift to her.
So I thought that if I made that quest more important, I would deepen the story. I decided that Casey had recently had word that her father had died some time earlier. But all that did was make the whole opening a downer. The comedy went away. I think that kind of character development probably belongs later in the series.
I think the secret is not to look to the detective for depth, but to the victim. In this story there are three victims, and two of them are stupid criminals who are kind of the flip side of Mick and Casey. ("There but for the grace of God" kind of thing.) I'm even thinking that Mick and Casey may rescue and help the second one. Certainly, though they are the only ones who care about these admittedly no good murderous varmints.
So: for depth, look to the victim. (And remember that the victim may be someone other than the person whose murder is being solved.)