I believe the hero modes are not supposed to be stacked. The hero modes are something like a few shots to complete except for weapon X, and have a story or animation sequence and call outs that do not make sense with stacking. this should not have been forced out in the shape it is in.
I have no idea why Stern, or John Borg does not say what is planned for the game, ie what the rules will be when finished. Also, I have no idea why this should be so difficult other than the new guys do not know what they are doing. It's very frustrating. I kind of think, in my mind, these new code guys are some type of comic book nerds who have not the first idea of pinball and maybe not even any idea of how to program.
for example, if the designers wanted to light this insert, if that switch is hit two times this call out and this animation and this amount of points and this other light sequence will occur. Whatever the case may be. I would think that by this point in the game we would be well along better than current and that a new code update would bring less hair pulling an emails to Stern.
It sound as if John Borg is not happy with what's going on, it's out of his hands in a way, he is not coding the game, he handed off that duty to a group of programmers who have never done this before in their life. I'm sure Borg didn't want at this point to still be trying to figure out what the rules are going to be.