No, obviously it's harder to find two old Korean people than one old Japanese person. Everything you've listed is hundreds, thousands, or millions of times more difficult than the young-Arab-man case.

Suppose you take down a plane with a young Arab man, and then you want to take down a second plane. There is a neverending stream of similar men willing to do the job. If your strategy requires you to use elderly Korean couples, you're done after the first plane -- you'll never find a second one.