Honestly? I think writers should be free to write what the hell they like and not be constrained by rules, especially by a genre with 'punk' in the name. I do prefer worldbuilding to be consistent, and justified within the logic of the story, but beyond that, anything goes. And you definitely don't have to include all the standard tropes. It's about a Victorian sensibility, optimism, and adventurous spirit, but twisted and 'punked'.  There's a darker side of Steampunk, where the optimism is seen as hubris, and the sense of adventure is seen as mad scientist or whatever. For myself, I'm pretty sure that my novel is fantasy, not steampunk, and I don't care. I also don't care whether there are corsets at all, never mind corsets worn on the inside or outside of clothes. You must do as you see fit, but I write what I want to write, and let the world deal with the results.  ;)

Best of luck with your steampunk screenplay!