Well i don't see how Mike would want us to see how he got revenge on Fabrizio.

They should release a new DVD of the trilogy while the film is in the cinemas.

And they would restore the deleted scenes and put them back into the DVD's.

The revenge in Part II seems more fitting than seeing Mike kill Fabrizio himself.

Could it be 4 ideas?

1.Flashback scenes will be during the end of prohibition and during the end of the 70's.
2.The actual time frame would pick up right from Mary's death to Vincents death, with some major skips in some unimportant years.
3.Francis Ford would stop being cheap and actually hires Duvall and uses him some how (Maybe how he died) kinda Mike thinking of Tom.
4.Vincent Mancini meets Grace Hamilton again and he lures her into the underworld.