Sure, anythings possible with conversions. If you like the Esci Polish Lancers, you could put their unique heads on the 17th torsos and use the falling horses and/or the LW/EVO prone horse and rider to make some casualty conversions. A little paint and voila!
The new "Into the Valley of Death" set opens up lots of new possiblilities for foot Cavalry Casualties too.
Hopefully someday S*R or HaT will make new Polish Lancers. They certainly deserve to be immortalized better in plastic. But if HaT does it first, they'll never make casualties. Their recent forum polls indicated Napoleonic collectors didn't want casualties so, you'll have to make conversions if you want any. And remember, my point here is to make Cavalry Casualty conversions, not whole armies.
Airfix already has casualty horses and downed riders in their French Cuirassier (light blue) and British Hussars (red) sets that could maybe be used with S*R's. Even Airfix's recent re-release of U.S. Cavalry in a nice mid-blue has the best downed horse which has already made it into my S*R Cuirassier stable. The U.S. Cav horse has very simple accoutrements, so it lends well to adding more Napoleonic saddlery.