My first pass at a design would be to see if a gas operated system can be designed for pistols. Why invent something that already exists. If any of the multitude of gas operated centerfire rifle designs is scalable, start there.
Just a thought and totally useless as an option for me as I work through the decision making process of enterring Bulls Eye competitions with pistol or revolver.
But we may some day see it, and you heard it first mentioned here