Playmaker already includes some "under the hood" method of having the defense recognize the difference between WRs, TEs, HBs & FBs. How about having the number of WRs key defensive personnel packages? For example, 3 WRs call for defensive plays from a list nickel packages; 4 WRs get dime packages. As a possible additional step, have the offense then read the number of men "in the box" and go to a short (3 plays?) list of audibles run with whichever sets of players is on the field.
As a complete non-programmer this seems really easy to me!