This one comes and goes from my list to implement, but it hasn't happened because of the footwork involved, plus overhead. Each command would need the ability of checking whether or not something else is killing it... *between each and every action*. This is a time penalty that everybody must incur for a feature that very, very few will ever use. Probably the best way for now is that if you have that rare stubborn command or two that may need to be killed (long loops, for instance), I would have a variable that's checked within the loop that's set wherever you want to stop it from. That's basically what would be happening behind the scenes, but not unnecessarily in the background for each and every action in every command.
Hope that helps!