I just got my 1805 French in greatcoats, and unfortunately the officer wouldn't work very well;'he just has a bandolier with his sword scabbard, and what appear to be rolled up trousers.
The Russian officers had a sash and their swords on a belt.
As for the musicians, they have epaulettes (which I suppose you could trim off) but then they still have the wrong webbing and a very non-french look.
In fact the only suitable figure I can think of is the drummer in the rather flawed Italeri Prussians set, and he's a big boy. Still, I guess a drummer had to be fairly sturdy to schlepp his drum along.