Wow, this was a really interesting read. I've always thought that 'Crusaders versus Black Falcons' was a bit over simplified and cartoonish (not a bad thing for a LEGOverse). Even with my moderate knowledge of medieval history, this all seemed a bit off so I've always thought of it as: all the LEGO soldier with the same torso are mercenaries employed by a king, lord or whomever. Said king would of course provide a tunic with his coat of arms on it to the soldiers he's paying to protect his castle, land and serfs.
I've thought that to be an acceptable combination of history and hollywood and it put's my brain at ease.