Well the important thing to remember is the council already had evidence of Naruto being a hero by him defeating Pein. They knew roughly just how powerful he was, yet still went in different directions twice.
There's also the Fire Lord himself to consider, as apparently he has some final say over who the Hokage is.
While Naruto is probably strong enough to be the Seventh, there's a pretty compelling argument, that he's not quite mature or wise enough. Hence, I would think Kakashi would make the ideal transitional Hokage from Tsunade to Naruto. And unlike Naruto OR Tsunade, Kakashi would understand like the 3rd, that yes being Hokage sometimes makes ugly decisions.