They can gauge the pull all they want to. It wont turn a clean shoot into a crime. If it was within the self defense act, it doesnt matter if you have a 3 pound pull, a 12 pound pull, or hit the guy with a 12 pound hammer.
Many believe (myself included) that any tampering with a gun can and will be brought up in a court of law by a prosecutor looking to hang someone and make a name for himself.
He will try to convince the jury that you were looking for trouble, that you had your gun made super sensitive and quick to fire. You rolled your own, you carved 'death to commies' on your grips, whatever.
One great point I read (may have been Massad, not sure) is in a civil case, you will be asked how many times you fired etc. There is a fantastic chance that you will not be sure. A lightened trigger may lead to the jury believing you 'accidently' fired the last shot that killed the perp.
Then there was something about an accidental shooting and insurance coverage that I don't quite remember (help me out here guys!). What I remember is that if you needed to defend yourself, you want the jury to believe that every shot was a necessary shot to stop the threat. If there is a chance that the gun discharged one extra time, and you have a trigger lighter than the factory engineers determined was a safe and usual trigger pull, you are in a deep hole and fighting your way out....
In the end you gotta do what you think is right, and if you ever need to put a man down I hope everything works out for you.