Sasuke's plan to be "hokage" is probably based on three things: Itachi's truth, Hashirama's description of a shinobi and Madara's past, and finally the idea of revolution.
After Sasuke heard the entirety of the truth from Itachi, he took to heart the thought of one man in the shadows that, through his own sacrifice and skill, controlled a situation (Itachi averting civil war in Konoha through the Uchiha massacre.) Hashirama's story added to that by teaching him past mistakes made by kage and Madara alike, in addition to the start of the village system. A "dark will of fire" was then burned into Sasuke's heart. Finally, the idea of revolution, metaphors included, lend to the opinion that...
The revolution is the dark flame that Sasuke intends to spread throughout the ninja world, his twisted interpretation of the will of fire. This has been metaphorically hinted at through Sasuke's gradual control of the black flames. Sasuke started off with wanting to destroy everything, which amaterasu essentially does, but now he wants to destroy and rebuild, meaning he must control the flame (enton and kagutsuchi essentially allowing Sasuke peerless manipulation of amaterasu's flames.) If revolution is the flame(火) that Sasuke intends to release upon the world, then he himself is the shadow(影) that will manipulate things (a la manipulating enton) from behind the scenes. The "Hokage"(火影) the person who starts and fans the flame of revolution, and once the old order has been reduced to ashes, he will put out the fires by manipulating the people from the shadows.
But, this is only my interpretation of it. What do you think?