The only flaw with the plot we are talking about is that most if not all of the people who tried to whack Michael and whacked Mary did get taken out in GF III before Mary got killed. Zasa, who tried to kill Michael, is whacked (along with "The Ant") at the parade. Don Lucchese is whacked by Calo after he Lucchese had the assassin kill Don Tommasino. Don Altobello is poisoned by Connie. Who is left? The assassin is killed by Vincent, and the "donkey-boy" might be left, I can't remember. Oh, and Al Neri hit the archbishop, and Keinzsig got rubbed out as well.

The enemies that hit Mary are wiped out...I'm not sure how they could handle this.