I love the banneret as a concept, but I absolutely loathe the execution. The main problem of the original class is that Rallying Cry is not good until you reach higher levels and you only have one use of it, Royal Envoy feels more like a ribbon feature, and Bulwark is so specific in its trigger requirements that you may play an entire high level campaign and never successfully use it once.
With my rework, I tried to make the features more useful and their use more frequent, while also maintaining as much of the original concept as possible and striving to keep the class simple (without adding unnecessary stuff like a banner mechanic, warlord-like maneuvers or anything like that).
Art credits: Purple Knight by BryanSyme
Looks good! The only point of critique (other than features in 5e not usually interacting with the inspiration mechanic, but that seems to be changing for 5.5e) is that Inspiring Leader is already the name of a feat, and Commanding Presence is the name of a Battlemaster Manoeuvre (which can be gained through a fighting style or a feat). This could cause a character to have two features with the same name on their sheet, particularly because those abilities play to the same theme (charismatic leader). I don't know what I would change the names to, though.
That's 100% a valid critique! I'm good at thinking about features and balancing around, but when it comes to names, I kinda suck. Those were the first ones I thought of and I probably didn't realize I got them from elsewhere. Should've paid more attention about that. Maybe I'll reupload the class with some names different, if I can think of a valid alternative.