Norris was a middleweight kickboxing champion in his heyday, and was supposedly the first guy to ever use a reverse spinning round house kick to the head in competition successfully.
Norris has also undertaken to study Brazilian jiu jitsu with the Machado brothers, and from what I read, has become fairly proficient at it.
Bruce Lee while a phenomenal martial artist did not enter competitions and was only witnessed a couple of times in actual fights, which he won handily. So there isn't any real way to judge how he would perform in the UFC, although I'd bet that he would fair well because he was a true student and would have learned everything available to him about Brazilian jiu jitsu and grappling in general. In fact, before his demise he had already studied judo with Gene Lebell and was beginning to study more grappling and wrestling. His book, the Tao of Jeet Kune Do, actually has rudimentary drawings of moves taken from his studies of wrestling and judo.
Both Norris and Lee, I believe, would have been great competitors in the UFC but only because of their willingness to learn and train. The other martial arts movie stars out there like Van Damme and Seagal would get smoked in the UFC. Including Snipes, haha.
As for limiting nerve strikes and pressure points, there are no prohibitions against striking certain pressure points on the body right now. Thigh kicks strike the area of the common peroneal all the time. But if you want to spend your time trying to hit four or five minor nerve points on the arms and chest going for the pressure point KO be my guest; in the meantime be prepared to get KTFO by a punch to the jaw, thrown once with bad intentions and without following a sequential path around the body known only to true masters of karate-do!