Why did Sherlock still make a fake death if Mycroft could manage to negotiate with the sniper and assassins and he could just pay a bunch of homeless to act as witnesses to Sherlock's death. It would make it easier for them than setting up a "stage". Did I miss anything?
They had to convince Watson. If Watson, Sherlock's closest friend, can truthfully say that he saw Sherlock die in front of his eye then that gives credibility to the story. Having a bunch of homeless people say the same thing doesn't have the same impact or authority.