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).
I like this! I tend to be very picky with other homebrew but I quite enjoy this. I've been of the opinion for a while that more fighter features should proc off of second wind and action surge. I especially love that you referenced both indomitable and inspiration, which I feel are often overlooked. Good job!
I wrote a full Commander class with the same vibe a while ago because I enjoy the trope but don't like the other warlords out there (kibble's is my least favorite. I also dislike warlord as a class name but that's just me). But I'd play this
Indomitable is actually referenced in the original Banneret feature (Bulwark), but it has such a contrived trigger requirement (you and an ally both failing the same mental saving throw) that you'll rarely if ever use it outside of white room scenarios. I just replaced it with giving inspiration, which fits the theme of a charismatic commander inspiring the troops, as well as having a much broader use in the actual game.
What's your Commander class? I checked your post history but I can only see your barbarian subclass.
Late response. Reason I haven't posted it is because I've been reworking parts of it I dislike, especially Rally and the subclasses, but there's an older version of it on the internets. I'm definitely keeping the directives though
Changed the names of two features (Inspiring Leader -> Swift Strategist, Commanding Presence -> Dominating Stature) as they are already used for other existing features.
Nerf: Changed Vanguard to only affect saving throws against the frightened condition (instead of charmed and frightened) and only if you're not incapacitated.
Update v3
Buff: Rallying Cry gives a bonus to attack and damage rolls equal to the Purple Dragon's Charisma modifier.
Buff: The upgrade to target two allies with Action Surge has been moved to 15th level (was previously 18th).
Buff: A new feature for 18th level lets the Banneret protect itself and its allies from incoming attacks.
This will probably be the final version of the subclass, as included in my Tavern Tales compendium. Click on the link to read the wondrous item related to the subclass, as well.
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.