So what if in the heat of the battle in Waterloo, Napoleon dies while directing his troops? I'm assuming the French lines will fall into disarray and collapse faster than OTL. But what happens afterwards? How will this affect Napoleon's legacy?
Well, he doesn't go out like a bitch on some random island in the middle of nowhere, and instead dies heroically trying to restore his Empire. I suppose that makes for a better story.Aside from that, little changes about history. Not like he did anything of any relevance on St. Helena.
I think he's remembered even better than he is IOTL. He won't be the man who died, sick, fat, and broken on a remote island, he'll be the valiant warrior who fought to his last breath for France and died the way he lived, at the head of an army.
His supporters will hold him up as a hero, martyred by the forces of reaction. In short, I think the Napoleonic legend is stronger in this timeline.