The schabraque was anyway part of the gala uniform and with the erratic sate of furniture at the end of the napoleonic wars i'm certain french hussars had it and the sheepskin together. Besides it can also be left to the trumpeters. They usually had a flashier dress even in the field. The plumes can be trimmed to make just a pompom. The rouleau shako was much more typical of the 1815 campaign. Before it was certainly given to some regiments as the 7th but not all. And yes the guides heads are perfect for this shako. Just give the hussars heads to them and you have excellent french chasseurs a cheval (well without the lance)
can you proof your statement of the expensive shabracke insteadt of the sheepskin with a (primary)source? Of around 500 paintings I have about the different regiments I have none with the shabracke as you mentioned it.
Like that I can't although I seem to remember an image with the french 3rd hussars using schabraques as late as 1814 in a book, but didn't search thoroughly
What I say is that the way supplies were either in Spain for most of the war and in 1813/1814 it would not be out of hand to think that strict regulation was not available. As an example most hussars had either pelisse or dolman and there were many regulation items unavailable.
The regulation and the actual field dress were anyway very different.