Admin Notes
To the specific suggestions:
1. Having specialists based on package is feasible. Really it's a question of whether or not coaches want the extra work that would come along with such a feature.
2. Having specialists based on play or play type is more problematic, since the other team's ability to adapt is currently based on package rather than specific players in the game. Doable but a lot of work.
.
Overall it doesn't seem like there is a ton of interest in adding this to the game, and given the effort it would add to coaching I'll decline to put it in.

Comments
Coach Clipboard: Please count vote as neutral. Think it's a good one but does add complexities. On the positive side you could add a long passing package, a blitzing package, inside/outside running packages, TB pass package, goal line package for best blocking TE and strongest TB with mostly runs (advantage being not have to assign them as GL specialist if want the other players for other GL plays), etc. I'm guessing most coaches would still rely on base offense/defense but mix these in some. To answer Andy's comment if you write the packages specifically enough then mix them into the situations could work nicely. To answer Ark Z's comment - yes if the sim recognized the tendency it's the coach's own risk how much they tip their hand. On the negative side I'd guess it would be very difficult to program Bob teams to use the feature, so would give the human teams unfair advantage unless Bob teams used them. For Bob teams, Andy would probably have to write a dozen or so specialized library packages that the computer would decide if it wants and assign players to based on roster strengths. Lastly, if this was all done, would have to see how this worked with situational specialists.
Michael Scarn: ================================ As far as I know, I can’t control how often a play is run based on who is in the game. I might want to blitz more frequently with OLB4 in the game. Other scenarios I don’t think are covered by substituting: I might want TB2 and TB3 to get around 10 touches each, but want TB2 to run it up the middle more and TB3 to run more routes. I might throw it 50% of the time out of every package, with a mix of screens, but would rather TB2 stay in to block or run draws. A TB3 package might also include less midfle runs. I might have a fast WR3 that I’d like to run more deep routes in a 2 WR formation. I will run deep routes out of other packages, but include them at a higher rate in a WR3 specific package.
Arkimedes Z: If the sim only brought in certain players to just blitz or just catch passes, wouldn't the opposition get a boost by knowing which type of play is coming? That said, it would be nice to adjust pass/run ratios (especially college), if one of your QBs is a better passer and the other a better runner.