You may also notice that the Fourth bares a striking resemblance to the Akatsuki member known only as Leader. I have my own beliefs on the identity of both of them. When Sasuke uses the Sharinghan to enter Naruto's mind he meets the Kyuubi, who makes the comment that the Uchiha clan bares even more cursed blood than him. Only one person has been shown to oppose the Kyuubi and that's Yondaime Hokage. I believe that the fourth might very well be the Uchiha Madora mentioned by the Kyuubi. He may be a wolf in sheeps clothing. I think he struck a deal with the Kyuubi and then later betrayed him and sealed him inside Naruto in order to come back and aquire that power later, as Leader seems to be doing.
More evidence on this is Yondaime's title. Yellow flash. I think more than most realise was revealed by Kakashi Gaiden. It showed that Kakashi was vulnerable when he first used the Chidori because frankly it involved to much speed and momentum for him to keep up. That is before he aquired the Sharinghan! Even Haku who used a Kekei Genkai could not move as freely as he would have wished when he warped between mirrors and more or less kept in a straight line. Therefore the only truly concievable way Yondaime could warp between his special kunai as effectively as he did in Kakashi Gaiden would be to both tap into the chakra tags on them as well as use a Sharinghan to give him an edge.
Kakashi earning the Mangekyou Sharinghan was significant in more than one way. His best friend died a long time ago when he first recieved the Sharinghan, therefore either Itachi's story of how to obtain the Mangekyo is completely false, making one wonder HIS true intentions, or there are other ways to achieve it. After all the only time it actually showed him killing ANYONE was with his Tsukyomi, a technique which could easily allow him to create a false story to scar Sasuke for whatever purposes he had wished.
Another important revelation brought on by Kakashi obtaining it is that the form it takes can differ from person to person. Leader has a ring around his pupil, this could very well be a mangekyo sharinghan. I also can't help but notice that Itachi seemed to come to work with him fairly quickly. I wouldn't be to surprised if Itachi is out for revenge but not powerful enough and is therefore trying to get Sasuke to gain the needed power. Surpass me so that you may surpass our enemy sort of thing.
Yondaime was also prevented from being resurected by Sarutobi, when Orochimaru started pulling out old Hokages. It wouldn't be to shocking to me if that last box wouldn't have worked anyway. That was also important because it showed that when resurected from the dead people still had some free will. The First and Second had limited free will but they were still able to speak freely with Sarutobi and even apologize for any trouble that they had caused him. Yondaime could have very well found a way to resurect himself and kept his free will. I again would not be shocked if a bit less logical conspiracy theorie that Orochimaru resurected Yondaime in some sort of plan for world domination and later lost control of him.
I may have read to much into it, and it is true that I have an overactive imagination but that's who I believe Yondaime really is. I see no evidence that they are related but think that Yondaime resembles Naruto because it makes him a better ultimate villian. The honorable thing is more than likely merely to build of tension for the inevitable fall. Make him seem honorable and give make him similiar to the main character, adds a bit of emotional content.