I could imagine this system, but,
I found something that said "Troopers" were called "Dragoons" because that is what they were,
Lance Corporal and Corporal, are they not the same as the later British light dragoon ranks during the Napoléonic Wars;
Lance Corporal of Horse, and Corporal of Horse, Staff Corporal of Horse? I think at least one of these is fictional,
And I also believe there were no Serjeants or Staff Serjeants. Not sure, though. :S