Keeping Jackie around for a season or two would have amplified the Junior/Tony crew rivalry. It would have been interesting to see if Tony would have undermined Jackie's authority. He was lying to Jackie about the Hasidic motel deal early on. Who knows what else he would have run behind Jackie's back.

In hindsight, I think the early demise of Jackie was necessary. From a plot standpoint, that real threat and tension of Tony and Junior going to war was necessary to hook viewers. I remember watching the first season thinking Junior wasn't going to make it past the fourth episode, and again in the season finale. Besides, elevating him to the upper echelon of the DiMeo family made the series what it was - a guy trying to run both a crime family and a real family.