There's an old erotic story where a couple visits an adult videostore and he explains to his wife what the gloryhole is for. Together at home they set up a fantasy in their garage. He cuts a gloryhole in the side of a huge cardboard box. When he gets home from work the next day, she has agreed to be hiding inside the box to give him a gloryhole blowjob.
Of course, he gets caught in traffic. Meanwhile, a neighbor comes in the garage to borrow a tool (hanging just over the box), a repair man comes by to fix the electrical box, the wife performs, word gets around, and when the husband finally pulls into his driveway there's a line of men and teenagers leading into his garage.
That "fantasy gone awry" idea could also be staged for a video series in a variety of settings, like a backyard toolshed or an indoor closet (remove the door knob assembly to create a hole without destroying the closet door--something houseowners would avoid).
It also offers a variety of casting options. A girl who would suck many cocks when she's only expecting her husband's could be played either as dumb and naive, as easily turned on and losing control of her impulses, past her prime beauty and desperate, or just plain slutty.
Within the "fantasy gone awry" premise, it's easy to involve other fetishes, like incest situations, intentional wife-sharing, voyeur husband peeking in secretly on the wife's side, interracial, even shota.
There's also room for a sequel or two. In the sequel, the husband tells his naive wife all the cocks (in the first video) were him, and she was so good he could get hard and cum again after only a few seconds break when he would briefly pull out of the gloryhole. Then in the sequel, while she's inside sucking, he's actually taking money from the guys he's lining up for the gloryhole. You could even shoot some location scenes with the husband recruiting guys from bars, gang streetcorners, locker rooms, homeless alleys, etc.
