I would simply have made the manga move at a slightly slower pace. I wouldve spent more time developeing characters. I wouldve created many characters and developed them, so when the war came around, i could kill them to make the war feel more dangerous.(as in this war tens of thousands have already died.....its just they were unseen, undeveloped characters.)
I wouldve used the edos, to take out some developed characters, and become developed themselves, then would develop/ progress another character more.
For example. I would develop say omoi more(to the point we see how strong he is)(lets just say he is k11 strength), then in the war have a new edo(say pakura of scorch style, become developed, by killing some strong developed people (like omoi in this scenario). Then i would use the newly developed character(pakura) to be defeated by a character considered more inferior(say rock lee), to make that character(lee) show more signs of power and character development.
To put it simply, i would change the manga to be more like onepiece with the character developement(as kishi doesnt take the time to develop more characters for the main characters to overcome.
Naruto+One Piece character developement=incredible manga>>> One piece
One piece=Naruto(as they are now)
One piece has good plot, but excellent character developement, while naruto has above excellent plot.(one piece doesnt keep me on the edge of my seat half as much as naruto, but is much more rich overall)