You're over exaggerating. Exploiting mismatches in the post and exploiting mismatches at the point is apples and oranges. Point guards initiate the offense farther away from the basket- where teams on the defensive are able to use the concept of team defense more often and more effectively by cutting of penetrating lanes off the ball and keeping the point guard out of the paint.
Sure it does leave the wide-open threes on occasion- but most of the time the defending point guards are beaten anyway because of a good pick that is set (even if the defending point guard is very quick;90% of dominant offensive point guards initiate the offense through the pick- therefore most of the reasoning behind stopping the point-guard has to do with an adequate mobile big who can hedge effectively enough for the point guard to recover going over/under the screen).
Am I saying you don't need an decent point guard and all you need is a great defensive big man? No i'm not saying that at all. What I am saying is it's kind of foolish to be so pessimistic on the Neal situation.
Some of you make it sound like Neal is going to face Russel Westbrook in a one on one 82 game series next year to decide the Spurs' fate. That is not the situation.
The real situation is that Neal will have to battle recovering effectively through variety of screens for 10-12 minutes in the compe ive games and 15-20 minutes a night when the game is out of hand. I think he's more than capable to handle that load, especially with the help of his teammates on the defensive end.
There's not enough evidence to say he can't do the job like you're assuming. In my opinion, stopping point guards has more to do with your big's ability to hedge and recover and at the same time, defend the paint by contesting effectively without fouling. Because point guards will and do get in the lane, whether Bruce Bowen or Gary Neal is guarding them because of the screen and poor defense by the helping big.
On the contrary, in the post is where it's much easier to exploit mismatches because of how close it is to the basket ( where there's less help behind the defender and it's where the most efficient shots are scored). That is why team's with dominant interior presence usually get very far at the end of the year because it's the hardest to defend because of how close it is to the basket and how far the help has to commit- only to slightly effect the situation because of the size of the post presence and because of how it leaves shooters wide-bare naked open.