I really disliked the fact that Michael "passed on " the power of the family to Vincent.It was not a smart move and it just seemed "out of character" and lazy for Michael.As for my answer to this question: i believe Tom would have disapproved.
Who do you think that he should have passed it on to?
Im not sure if the rules of the mob allow this,but i think with time,Michael maybe couldeve trained and taught Connie to take the reigns.In part three it already shows how ruthless and cunning she can be.Also it would have been a fresh twist having a female "run" things.Just a thought.