Steve,
In your first line of discussion, suppose there were no obstruction, merely a runner trotting toward home. If she decides to not proceed to home but to just divert into her dugout, would you not invoke 8-7-U? The gross miss vs. pass & miss (line of discussion 4) would mean that no active runner can EVER have 8-7-U invoked, only one who is not active and merely leaves her base. Would you apply this to a BR also?
I like #2 due to the discussion that could ensue. If entering the dugout takes away the runner right to touch home, but you have now declared her out, but that is not one of the exceptions for obstruction, so you now award home, a base she is not legally entitled to touch...
