I picked up 1897 Nixey Callahan as my AAA 2B. He is an okay hitter with no power or speed, who can play every position (poorly) but catch. Though he has thus far exceeded expectations. He also pitched 189 mediocre innings that year. Mediocrity would be a big upgrade over my two AAA pitchers. Any way to get him on the mound in sim games?

No.

I think I once had a 2B named Doc Crandall who also pitched in his RL season and was told by WIS admin that you either draft the guy as a position player or as a pitcher, but he can't do both.

What if you were actually allowed to draft both versions of them?  The pitching Ruth for the hill, and the OF Ruth for the greensward? You would have paid the price for what they can do, if that's what you wanted to do, fatigue would not be out of whack.

Couple things:

1.  WIS did try a few years ago to allow fielders to pitch but they screwed it up.  We blew it up in the testing phase and they abandoned it.  They couldn't program the system to only allow players with IP to actually pitch so basically anyone could pitch.  They couldn't get non pitchers to be bad enough so guys like Larry Walker were pitching complete games with ok stats.   I remember one team in the test version spent 78.8 million on hitting and won like 135 games.

2. You can get pitchers to play the field but it is complicated and it is so hard to do, no advantage is gained.