So long as it's not "magic" and there's no implication it's magic, but rather some extremely ill-defined "internal energy" or the like, and it's PHB class, that'd probably be good.
Honestly I think at this point, we need to just delete the Monk class entirely for the sake of D&D. There's no other class I'd say that about with certainty. It's a weird little orientalist blob and 5E 2024 didn't fix it, just made it more mechanically effective and very slightly less orientalist (but not really). Let's kill it, and take its stuff!
Then we can have a class which could do armed or unarmed combat, armoured or unarmoured (really work on the balance so it's an actual choice, maybe subclass-based), and which has a name like Warrior (i.e. a name as broad as Fighter), and one of the subclasses is Monk (because D&D Monks are indeed "Warrior Monks") or similar, and has most of the trad Monk abilities (we don't need to replicate every subclass).
We probably also need a Rogue/Ranger/Ninja one separate from that unless the subclasses are absolutely incredible, depends on how skills are done in part I think. In 5E we would - maybe not in 6E.
I think it exists solely so Numbers Go Up, and you get a feeling of progression.
Now, does that mean we don't need it? Hmmm perhaps perhaps not. I think we probably do with a level-based game because Human Like It when Number Go Up. Even monkey can count banana, wish for more banana.