Help me understand your expected results -- so, you DO NOT want a line for "all others" to compare to the selected Region? You ONLY want to see that Region filtered down in the subsequent views? If so, a simple action filter using the Region dimension should do just that. Perhaps I'm missing something -- a mockup of your expected results, or a bit more detail with screenshots may help as well.
Thanks for posting a packaged workbook -- I'll take another look after you respond. Cheers!