Don’t get me wrong—criticizing is way easier than creating! I think there’s a lot of potential here.
I think a separate subclass feature makes sense. Maybe at level 1 you get some (1st degree), then more at 6 (2nd), and 10 (3rd).
I think allowing EB to be used with appropriate maneuvers (melee/ranged) is enough. To me, that is what makes the subclass concept cool and unique! And if a player really wants, they can use thirsting blade to take an ordinary attack action with two attacks for their maneuver.
You might also consider writing some thematic invocations for the subclass too!
Final note: I write for a living. Don’t be discouraged! I’ve mangled things a lot, and somehow I still get paid for all the mangling. You’re doing this for fun! Feedback is a part of it—I only provided it because you asked, although I did go a little hard on ya.