And it's still a NO....his body and frame would NOT have have held up to the reckless abuse QBs went through in the 60's, 70's and 80's.
I'm trying to recall some of these huge solid QB's of the 60's, 70's and 80's that you are implying existed? Also, the players today on defense are a lot bigger, stronger and faster than many of the guys playing "way back when". Saying that 40 year old Brady has a "thin and frail frame" and the only reason he is still playing are due to the refs protecting him, as well as not getting hit by "huge" guys like Nitschke, really?
The rules protecting the QB may have changed since the 80's, but so has the size and conditioning of the athletes playing the game, including Tom Brady and the guys hitting him. I would even go so far to say, if those rules didn't exist, even the bigger better conditioned QB's of today wouldn't last long under the constant hits that they would be sustaining by some pretty big men.