A clever deduction and indeed yes it is true no doubt, though my personal experience with said knights is only partial. Regarding one's skills in the art of assassination however, I'd like to think I have my bases covered. Stealth has and will forever be a formidable skill whilst fighting or otherwise wishing one's self impartial to aknowledgement.. and in regard to your to your question there "is" infact a vast variety of figures to impersonate!
The common guard for one, a shuffling hunched-back hermit, a political figure (if the skill is high enough). Find the correct people to write with and I'm sure they'd allow you to impersonate there characters as well. Though do take into account that the ideal of impersonation isn't centered around the common figure; it leaves a staggering amount of room for development and creativity!