It's not clear how Bernard planned to meet Ben and Jo if Hank hadn't accidentally grabbed the woman's headscarf. The Arab man who yells at them is implied to be under Bernard's employ, so what was his original purpose? Presumably the Arab man would have found some way to threaten or inconvenience the couple, allowing Bernard to intercede and gain their trust. Hank's accident just so happened to provide a perfect excuse.
He wasn't looking for Ben and Jo. He was looking for a "suspicious couple." This is more of a case of Fridge Logic, because if Hank hadn't accidentally grabbed the woman's scarf, Bernard would have never met Ben and Jo in the first place.
And it's not established that the Arab man worked under his employ - rather Bernard was just asking him if he knew anything about Ben and Jo. On the other hand, there was a woman with Bernard which DID seem to be at least partly into his scheme, but we never got to know anything about her or her fate.
So the plot is to kill a Prime Minister. Does the film ever say WHAT COUNTRY he's Prime Minister of?
Why were the Draytons in Morocco in the first place? They had an assassination coming up in a few days, so what were they doing thousands of miles from the chapel that acted as their headquarters?
As the dialogue shows, presumably they went there to hire an assassin they'd been hinted at for their mission.