I could see that yeah, and upon rethinking it, the martial arts to gamage is much more similar to the hunter ranger thing. like, giant slayer or whatever. So, it's not unheard of to just tack on extra damage, it's just that with the monk you're doing it by applying the extra damage with another attack instead of ranger or rogue being through precision or the barbarian through rage. You could actually maybe make it so that the extra damage is considered a second attack that automatically hits if the first hits, that way you get magic item and ability score scaling. Then maybe just make it get combined with the triggering attack for overcoming resistances. I could see it worded something like this.

"Martial Art: Any time you successfully make a melee attack that deals damage, you lash out with a flurry. Make a second attack against the same target. This attack automatically hits. Combine this attack and the triggering attack's damage rolls before calculating resistance or vulnerability." (Or, leave them separate since they ARE two separate attacks, making the monk less effective against resistant enemies, but MUCH more effective at vulnerable enemies.)

Then still make it where you can't attack as a bonus except for Flurry, which requires a ki point, this removes the "every round free bonus attack competing with everything" and retains the option of a flurry attack (SINGULAR since it would also trigger your martial arts effect, making it effectively 2 hits) or a dodge or dash or disengage.

I feel this change would definitely bring the monk's baseline up significantly while maintaining the on-the-fly decision making that monk's are good at via ki-expenditure. :D I will say, I still like the idea of the styles i mentioned, but in hindsight, that's pretty much what the subclasses are for. Kensei is the weapon one I mentioned, open palm/hand is the mega-unarmed (Might want to make minor changes to the subclasses to make them work with the base changes, but that's a problem to tackle later.) But, then you also meet odd-ball ones like sunsoul or mercy where you are effectively allowing them to go full vegeta and blast ki blasts all over that scale much higher than originally planned and could make for a horrifyingly strong "archer" while mercy would become the best melee healer in the game by having good scaling on heals, with amazing mobility and defenses from bonus actions, and high damage throughput with the martial arts changes.