Pau has no where the devastating impact Kanter has on offense & isn't a great defender himself.
Kanter absolutely destroys teams in the paint, is unstoppable on PnRs (which creates gravity; if only OKC had shooters:

) & can space the floor all the way to the 3 point line if needed. Pau is a jump shooting big (mostly mid-range so not as valuable as a true stretch 5) w/ an average post-up game whose elite ability (passing) is marginalized unless the offense is running through him. (Let's not act like he's being used like Boris 2.0 when D-Worst was racking up assist from the elbow

)
Kanter in the Spurs system would basically be David Lee if he had range all the way to the 3 pointing line & was a more devastating roll man/offensive rebounder. (As it is, Lee is outplaying Pau

). Kanter isn't a passer but nor was Amar'e but that didn't stop him from be a devastating offensive force on PnRs. (Kanter doesn't have issues playing w/ a non-shooter like Dedmon as evident in the 2nd rd when he & Adams as a tandem absolutely killed the Spurs)
Speight can space the floor & pound the offensive glass better than Pau so if you're going to use Pau as a floor spacer while vacuuming uncontested defensive rebounds on the other end then I'm not sure how you could compare him to Kanter. Kanter destroyed Lee this past postseason & wasn't exactly getting killed on defense against the Spurs (He was holding his own defensively that he got to play 30 minutes in the pivotal Gm 5 while Ibaka was sitting out the 4th quarter & basically was responsible for the sequence that won them the game where he had two put backs & blocked Tim at the end of the game)
If Pau was even an average defender then you could have the case but this is just a case of where he's horrible at everything besides being an average rim protector.

(Pau is '05-'06 Big Z status (
http://bkref.com/tiny/SsFyG) unless he's playing point-center as the hub of the offense, which he isn't)
Why in the would Dedmon have to play a 2-man game w/ Porker?

(I just said he would be a PnR option)
Porker can run his PnPs w/ Aldridge while Dedmon sets off ball screens/pounds the offensive glass which is what Robin Lopez did & guys like Tristan Thompson have been doing for years.
As far as playing PnR w/ Dedmon, if only the Spurs had a guy called Patrick Mills who has been feeding Dedmon all season long.
The Dedmon/Lee tandem can be skimmed against in the postseason but it works fine now b/c teams aren't game planning for backup players in the regular season.

(Doc is a guy that exposes mismatches which is why he's basically the only coach that has made the Dedmon/Lee frontline seem unplayable)