I would also recommend that although it's not required, you should inform your opponent of your intentions. I realize that there is no rule requirement for it, but if this is supposed to mimic the real thing, your opponent cannot set his lineup fairly - as he would if it was a gametime decision in real life. I also realize there have been passionate debates about that subject before the pitch minimums were changed. Since you cannot have a late "scratch" and your opponents cannot react, it seems fair to me that if you go through the routes suggested, that your opponent should be able to prepare fairly.
By making the moves above, especially the waiver suggestion, you are in essence circumventing what the 40-pitch rule was designed to prevent. If Simmy ends up starting the pitcher you intend, how will your opponent be able to set his lineup?