The point is, first we should balance Champion against the most brain-dead BM. That is a floor.
If you want to do analysis of a fancier BM who uses things like Riposte, go ahead!
The BM who just spends their SD on getting higher damage numbers, rather than engaging with the the more tactical maneuvers
is the floor. Just using Riposte and Precision attack whenever they can is about the lowest level of engagement we can expect from a good-faith example player.
I never denied it. My point is, there is no reason why a player who cares about such things would choose to play a champion, so it doesn't matter.
Maybe they like the subclass abilities as more fitting to their character concept than the other Fighter subclasses.
How, when they can just play a battlemaster? There is nothing in the champion can do that a battlemaster cannot, other than serve as training wheels or allow combat passivity.
Extra combat style, specific synergies with some race/feat combinations, getting crits is fun, regenerating HP in combat . . .
Buffing the chamipon can only have two effects:
1) Increasing complexity, forcing a player to engage with combat when they don't want to.
2) Frustrate battlemasters, who, for all their tactical acumen, struggle to keep up with someone who does nothing but stand around hitting things with a sword.
1) Buffs don't have to be complex.
2) I think any Battlemaster player who likes using tactical acumen is not going to be using "total HP damage dealt throughout the day" as a performance metric. Even ignoring the more . . . tactical options that maneuvers can grant, being able to apply extra damage at just the right time is going to be more valuable than just getting it randomly, and tactical players will understand and value that.
There is no downside to bringing Champion on-par with a baseline low-engagement Battlemaster.
Instead of giving an attack at start of combat what if you grant +2 Attacks when using 2nd wind?
Personally I'd be against making second wind more powerful - it puts even more eggs in a single basket.
Actually . . . how nuts would simply granting the champion an additional charge of second wind really be?