I've got 1923 Jack Bentley and his .447 BA in a progressive, and I would like to encourage Sparky to deploy him as a pinch hitter. Is there any way to influence this, since you can't list a pitcher in the Pinch Hitting priorities? I have seen occasional opposing pitchers used as PH with effective results.

Set your whole bench to rest.

That's the only way.  If there is even a single bench player available, sparky will use him before going to your pitchers.

So if you set your entire bench to Rest, will Sparky use all your pitchers as pinch-hitters befor using any of your bench?

I don't know for sure - I've never pushed the envelope that far.

My general experience is that when you set a player to "rest" then Sparky will not use that player unless he has no other alternative.  I think if a position player were to get injured that Sparky would use a rested bench player rather than a pitcher to play the field, but I cannot confirm that from experience.

"I can confirm that. As for PH, I almost certain the SIM will only use Pitchers in your rotation that did not start that game as a PH. I've never seen it use a RP and I use this strategy a lot."

 So paying for George McQuillan's 44 IP season or Hal Haid 1928 for their hitting is a waste of money. I would agree with that even if they got 15 at bats during a season and had 6 hits -- which is unlikely. They don't have enough IP to stay in the game long enough to hit.

I used pitchers as pinch hitters last year with good results.  Here's the scoop:

Only pitchers in the starting rotation will pinch hit, your bullpen will not PH. If they have low stamina while resting between starts then they wont make good pinch hitters. so put your hitting pitchers at the back end of your rotation and draft enough innings. 
All of your bench players must be on rest. you must give up your bench, no defensive replacements no resting players in a blowout. players on rest will not PH even if your pitchers are used up.
Pitchers will only pinch hit for other pitchers, they wont PH for a weaker hitting position player.
This is a cumbersome strategy. I liked it when good hitting pitchers were a bargain. I dont recommend it now that their salaries have gone up. also not recommended if you have just one hitting pitcher, you really need several or else it's not worth the trouble.

Thanks all for the advice, even if it is discouraging. I intend to start the season with Bentley in the rotation, but not sure I will go this route to get him more AB's ... though I might give it a shot in some interdivisional games just to see how it works. I've also got 1954 Dusty Rhodes on the club, so I'm not likely to pinch hit Bentley unless Dusty plays the whole nine.