I am glad this planning was abandoned!
If I had not misunderstood, we would have missed out on, among others -
Fredo's welcome party! for Michael
Greene: Do you know who I am? I'm Moe Greene!
Michael: Fredo you're my older brother and I love you but don't ever take sides with anyone against the Family again Ever
Also I can't see Michael relying on the assassin to be someone in Moe's entourage
Michael undoubtedly would want the assassin to be from
his own men