Personally, I'd find it interesting to see, since the game is based in 1809, whether it will be featuring Portugal and Spain. Imagine 2v2 Battle - France, Bonapartist Spain vs. Great Britain, Portugal. That would be one hell of a site, but I really need to hear from the developers, if their focus is put in that conflict - The Peninsular War. This could be the Second Portuguese Campaign and the possibilities are plentiful.
Also, I would find it myself more interesting to add the Rheinbund faction as an ally of France. Wurttemberg Line Infantry, Bavarian Line Infantry, Saxon Grenadiers, Nassau Voltigeurs, Hessian Jaegers, Hessian Militia/Line Infantry. Yeah that'd be interesting, even if going a bit offtopic.