I understand where you're coming from and I wasn't trying to imply West was some kind of potential All-Defensive Team member; just that he's a strong guy, who moves his feet well, and has a good compe ive-fire that makes him more than capable.
The thing I worry about with Oak though is, I wonder if at this day and time you could get by consistently playing him alongside Tim. Tim's mobility isn't what it used to be and neither of them are guys you want straying from the basket. With the way the league is now, and if you're going to play with two shot-blockers, their skills have to either really mesh offensively to exploit the opponent or defensively to shutdown the opponent. Plus, the twin-tower look the Spurs modeled their first championship formula after didn't have to deal with the ridiculous rules changes defensively and were able to play a low-point ground-it-out affair because of it; those days are long and gone with the athleticism you now see in front court's across the league and the hand-checking rules on the perimeter.
And that's to say nothing of the personnel the Spurs have on this team. Maybe you solve the rim-protecting problem but you could be giving yourself a whole new set of problems offensively with the congestion in the paint; hard to have a score-first point guard, without a 3-point shot, that lives in the paint and a slashing 3-man in RJ thrive that way.. and that's to say nothing of Manu who's at heart a slasher himself.
The dual shot-blocker threat would be great; it's just got to be the right fit for the personnel and times we're currently in.