This project is actually half-way in motion, in collaboration with my cousin James.
The idea is heavily historical Narrativism. That is, the real history has a huge presence in the game, as if it were a player. Players will control individuals who, while fictional, could have existed at the time. Through their actions, they can change the course of history, for good or for ill, or they can utterly fail to. The Egri-style Premise is two-pronged: Is it right to fight for peace? Should the individual be sacrificed for the greater good? I perceive the real history of the Sengoku Era as a true story that provides very complex, nuanced, painful, and sometimes contradictory answers to those questions. Some of them make me sad, some of them make me excited, some of them make me just plain angry. Could it have been better? Or, possibly, was that the best it could be, and would trying to change it only make it worse? The big ambition here is that by playing the game, you get to pass a judgment on the history, and the history gets to pass a judgment on you.
The game will have a central GM, whose job it will be to represent the NPCs based on historical guidelines, breaking from their historical character only when sufficiently influenced by the actions of the PCs. When a PC is killed or otherwise taken out of the story, his player becomes GM and the former GM creates a character. Thus we have a rotating-GM setup with a persistent world, allowing you to play your own, unique take on the Sengoku Era from beginning to end.
I'm excited about the conflict system, which uses "skills" ranked on four steps: the Path of..., the Art of..., the Mastery of..., and the Truth of...
Path gets you a d6, Art a d8, Mastery a d10, and Truth a d20. Highest roll gets their Goal, with consequences inflicted on both sides determined by the actual numbers rolled. This creates an interesting setup in violent conflict--it's not enough to say, "I kill him!"; we have to know why you're trying to kill him. If you roll higher, you get that why; whether or not you actually kill him, and whether or not you suffer injury (or some other consequence) will be determined by the actual number you roll--you might get your Goal and not kill the guy, or possibly even kill the guy and not get your Goal! Truth always gets its Goal, except against another Truth, which goes into a gradually escalating duel to determine which one is really the Truth. You learn the Path from instruction; the others are awarded by the GM when your character demonstrates that level of prowess.
It's going to have, gasp, character classes: Soldier, Mercenary, Samurai, Ninja, and Monk (in the Ikko-ikki sense). Each of them has an Essential Quality stat. The EQ of a Soldier is his loyalty. The EQ of a Mercenary is his independence. The EQ of a Samurai is his honor. The EQ of a ninja is his detachment. The EQ of a Monk is his holiness. You gain and lose EQ points by demonstrating that quality and by demonstrating a lack of it, respectively. You can also "burn" an EQ point for an automatic success, of course requiring that you act in a manner against your EQ. If your EQ hits zero, your character must be written out of the story in a manner in accordance with the EQ (for instance, a Samurai who has run out of honor will probably commit seppuku; a Ninja who has lost his detachment will probably slip up somewhere, and fall prey to traps or counter-assassins).