I don't like rules that protect you from yourself.
One fighter getting KOed too much for your liking? Stop giving him fights (cut him), or make him fight Jon Fitch. If someone wants to continue their career, who are you to stop them?
And how do you handle guys who take lots of blows to the head, but never get KOed? The long term effects of having a "good chin" and getting blasted 200 times over the course of your career might be much worse then having a glass jaw and only taking 10 good shots in your whole career (because you immediately hit the mat each time).
Those guys suing the NFL were hit repeatedly over a long period of time, and rarely got KTFO on the field (4 concussions in 120 games, while sad, is not frequent at all. I'd be more worried about the other 116 games, getting hit all day).