I know you can file this in the "things that will never happen file" but perhaps its easier than I realize and I think could be beneficial in some circumstances.

In one of my worlds, a future HOF pitcher w/ a 115/130 pitch count cruising in a 2-1 lead thru 6 came to the plate w/ the bases loaded and nobody out.  The pitcher had thrown 92 pitches to that point, so he certainly had enough in the tank to take him thru the 7th and possibly 8th inning if he got thru the 7th unfazed.  The sim pinch hit for him.

I don't know what the coaches pinch hit setting was at, perhaps it was 3 or perhaps it was more agressive and set to 5.  In the real world, w/ you ace on the mound, I'm assuming most coaches would allow their pitcher to hit and hope they didn't hit into a double play, then count on their Ace to give them another strong inning or two before going to a worn down bullpen.  A coach could always uncheck the PH button on the edit players page, but then what happens when the pitcher comes up in the 9th and you really do want to pinch hit for him?  Of course the coach could always lower his PH aggressiveness from game to game, but that's a bit tedious if you ask me.

Having the ability to set pinch hit aggressiveness individually could be beneficial in this case.  Say one pitcher you could set to 2, while others you may set to 5.  Perhaps there's a defense first C that your normal start and bat 8th, but you'd like to pinch hit for him more often and bring your backup into the game if you really need a key at bat, while you rarely want to pinch hit for your defensive SS.

I don't know how taxing that would be on the servers, perhaps too much to make it a possibility at all, but would give us more options for key at bats.

Couldn't you just change your PH settings before every game?   If you're starting that ace, lower them before the game.  

absolutely you could, I'd just think that would become tedious, plus how does that affect other positions where maybe you do want to pinch hit, or if your ACE gets hit hard early or you go extra innings, and now you've got a situation late in the game where you'd want to pinch hit, but you lowered the pinch hit aggressiveness for the whole team b/c of one player.

Changing one setting every 8 hours would not become tedious.  

OK, tedious is in the eye of the beholder I suppose.  But what happens when you drop it to 1 and you go extra innings.  Your ace has reached his limit, and now you bat your Long A man in the 11th inning becuase you dropped your PH aggressiveness for 1 guy?

I realize its small potatoes, and may not even be reasonable due to processing time it would take to properly implement, but I think it could be useful.