Interesting examples, but I'm not sure how to apply it to my program.
I don't have a global variable that allows you to "artificially" set variable firing rates, I have enemies on screen that equal the current wave (level) and each enemy should be firing at a different rate. I am not given the luxury of using a global variable to divide by, as I need the firing rates to be random.
If you take a look at my screenshot above, you can get a general idea of what I am trying to do. I need the enemies to be firing equal to their fire rates.