I'm glad you asked. I've been thinking about this a lot lately. This is what I'm thinking I will do:

I will have the basic rules, which are pretty realistic, and a heap of Optional Rules that allow you to behave like in the movies. That way people who want to play a "serious" or gritty game can just use the basic rules and have their tough firefights. If you want to play like a movie, the Optional Rules would over-power your character while firearms from normal people would be stuck back down with their 15% accuracy rate.

Here's an example of something I'd been planning. I was planning to, after I've reached a reasonable draft of the firearms rules, to write a pretty realistic set of rules for hand to hand combat, where hand to hand is useful for silent kills or for when you're suddenly sucker punched, but not effective for running up and trying to punch a man with a shotgun. However, alongside that, I'd have an optional ruleset for Mr. Miyagi-fu, where any successful martial arts attacks would automatically defeat anyone whose martial arts skill level is lower than yours by a certain margin, which would take precidence over the realistic ruleset when employed.