So, back to banneret, maybe the best feature swap would be:
Level 3: Knightly Envoy: You can cast Comprehend Languages as a ritual (using Charisma), swap one known language at the end of a long rest, and gain proficiency in two skills from: Insight, Intimidation, Persuasion, or Performance. One of those skills gets Expertise (doubled proficiency bonus).
Remove expertise in a skill and replace with:
Tactical Superiority: You learn either the Commanding Presence or Tactical Assessment Manoeuvre plus one other combat manoeuvre from the following: Bait and Switch, Commander's Strike, Commanding Presence, Maneuvering Attack, Rally, and Tactical Assessment. You gain two d6 Superiority Dice that recharge on a Short or Long Rest. At level 7, you gain a third 1d6 superiority die and can learn a third Combat Manoeuvre from the above list.
It feels like banneret's abilities, while flavourful, may be a bit limited. Use of group recovery doesn't even increase as your use of second wind increases. It's still just once per short rest. Is it really so good that it had to be that limited?
I just feel that Superiority dice, which can be padded with feats to cover everything on that list, would at least give a bit of warlord versatility.