I think 'Napoleon's Grognards' is a great name if you are aiming to appeal mainly to grognards, ie fairly hard core wargamers. If you want the game to have wider appeal, and shelf impact (will you be selling in shops?) you might need something different. I agree that the title should contain 'Napoleon' for instant recognition and impact. But you could use a more dramatic subtitle - how about something along the lines of (some of these are from book titles):
Napoleon: Anatomy of Glory
Napoleon: Clash of Empires
Napoleon: Crucible of Courage
Napoleon: Days of Glory
Napoleon: Days of Destiny
Napoleon: The Art of Victory
I think I quite like 'Napoleon: The Art of Victory'
Or you could go for something less dramatic, more descriptiive of what it does:
Napoleon: Battlefield Commander
Napoleon: Supreme Commander
Napoleon: Grand Tactics
Napoleon: Lines of Command
Napoleon: The Art of Command
Napoleon: The Art of Generalship
Napoleon: Command Decision
Napoleon: Command and Tactics
Napoleon: Order of Battle
'Napoleon: Order of Battle' is quite neat, a small play on words. You could then call the series 'The Order of Battle Series'; this first one would be 'Order of Battle: Napoleon', and your next expansion could be 'Order of Battle: Wellington'.
Whatever you decide on, good luck - looks like an excellent project.