Since that has been said to be a "never gonna happen" and "too cumbersome" a programming nightmare, what about a simple threshold figure of combined SP/BR. 

In a dropdown menu next to the base stealing aggressiveness setting. Like NEVER send a guy with less than "X" total SP/BR rating.

It could easily fit in the decision tree right after the aggressiveness setting has been checked and simmy decides to send a guy with 0 speed and 49 BR because, after all, you do have it set to Very Aggressive.

Or perhaps just add another tier like a 6 that is "stupid aggressive"...

If they modify any part of the stolen base logic, they're going to have to modify all of it.

In your suggestion, if bad base runners are prevented from ever attempting to steal, then the overall percentage of successful SBs is going to go up past the point of being realistic compared to MLB.

So then they'll have to modify the existing logic to throw out more of the high speed and high base running guys.  Or maybe make the guys just above the cutoff attempt more SBs and thus get thrown out more often.  Or just let the SB success rate move away from MLB norms.

If they're going to do that coding, might as well just change it to individual settings. And they've been pretty clear that will never happen.

Yeah, too much work.  They won't even program a HoFer to show the position he played the most at in his career (can't be that hard to program - they already have them wearing the hat of the team they played the most on)