WI: Napoléon & Joséphine never marry, Frederick, Duke of York, dies in 1803...

[Kingpoleon]

And Princess Frederica Charlotte of Prussia married Napoléon in 1805, as part of a deal with Prussia?

Instead of Austria becoming Napoleon’s ally, a militarily competent Prussia is made his ally and gains control of Germany. I imagine that much of Westphalia would go to Prussia, and Napoléon could focus on his favorite goal: Italy.