Three Musketeers, Guy Fawkes (English I know), Sharpe (again, English, but very much part of that milieu). That time period was full of intrigue, backstabbing (both figurative and literal) and killing to achieve one's wishes. Imagine something akin to the Thief games, but 3rd person with all the AC stuff. Feudal Japan is too obvious a move and quite frankly has been over done by Tenchu and other japanese games over the last decade. Ninja games are a dime a dozen, but a French ninja, that's original.
The games biggest hurdle will be how the character looks. It's not often a game with a very familiar character you see all the time on screen is replaced. The series revolves around (spoilers) the family tree of this assassin, so you're not Altair, but his distant decendant 600 years later, but it still will probably deal with the dude that was in the machine from the original and his story. So it will be interesting to see how people will react to it, since the last time this was tried was MGS2 with Raiden being the new protagonist, and that didn't go over too well.
I loved AC and even though the game wasn't perfect, it had a very unique feel to it. I've said before I love it when a game makes you feel like you're actually in a living world and you feel like you're going there when you boot the game. This was one of those games.