The smart part of sending Luca with his story is that he announced first hand to everyone that he would never go against the Godfather, making it believable that he is not coming in as a snake in the grass, but as a helping hand that would strike on command, for the right price of course. In the movie Luca is made out to be a loner, but in the book it says many times that he has a crew under him. Also the heads of the families being kill and the "baptism by fire" scenes are in GFI not GFII.
Luca had a crew? You'll have to cite those references. I don't remember them at all.
However, what the novel does make very clear is that Luca's loyalty to Vito was legendary in the NY underworld and he would never share that loyalty or any portion of it with another family. Sollozzo, Barzini, and Tattaglia knew this and would never buy Luca's cover story. The Don was slippin', indeed!
