This stroke me when I read Brockdorf's post about the F1 analogy.
In F1 they don't limit horsepower, because they don't cap what they can't control. It's as simple as that. Instead they cap cubic inches, width of wheels, minimum weight, gas consumption, number and size of wings, etc. All of which is easily accessible and controllable from the outside. No need to dig deep into the software of any microchips.
So for a start, why don't we put a limit on the maximum inner diameter of the hose? In combination with another rule stating the maximum pressure one is allowed as input pressure for the gun, this effectively limits the air consumption and thus the ROF. Of course this rule would blatantly ignore the specific problems with gas hogs and/or double staged balanced regs like the Armageddon. But it would be a rule which is simple, concise and easily checked.
Another option would be the basic design of the trigger, but I will have to think that over again.
Some more ideas: minimum distance between grip and front reg, as to force the player into an uncomfortable position (not a very good one, I know), maximum battery power allowed in a loader (I like this one)
I somehow suspect my post will be ignored and/or dissed.
But I would still appreciate some constructive feedback.