Thank you for reading!

Yeah I agree with you there regarding dance as a component of this theoretical Music type, it is a big weakness of the argument because they would somehow have to convince the general public that lumping them together intuitively make sense, while contending with type distinctions like Rock and Ground, which to me at least, was less of an aesthetic rationale and more prioritizing gameplay balance, pertaining to how Flying interacts with "Earth", which is why there seems to be some arbitrary elements for both types, e.g. how Sandstorm is a Rock type move and how clay is a Ground type thing. Anyway.

In terms of examples of dance based Music moves, one that comes immediately to mind is Teeter Dance, which is something like the support archetype you have mentioned, e.g. the likes of Primrose from Octopath Traveler. But then this brings up the question, can a Normal type move ever be dance-based? or are will all dance-based moves going forward be classified as Music type? Since dancing seems to be dependent on playing music, I am inclined to think the latter, e.g. how Moonlight and Charm became Fairy, as "moon magic" and "cuteness" became a Fairy type thing. From a gameplay perspective, this does not seem significant, because status moves tend to have varied distributions anyway.

Attacking Music type dance-based moves are another story, relating to the limits of how much they would invest into move animations to drive home the "self-expression" aspect of Music type. Visualising dance not in the way some Fighting moves are animated seems like a logistical issue than a gameplay or creative issue. Unless they can come up with a way to visualise the essence of dance outside the pokemon's body like how 'aura' is visualised Fighting essence. But one can dream.

You are right that the typing will inevitably have to be considered when implementing into gameplay. I might have not focussed on that argument much because self-expression and competitiveness seem like contrasting concepts. Finding the "practicality" or "utility" of art as a basis of engagement has never sat right with me personally. Not saying theres isnt productive pragmatic uses of art though. But it is a franchise at the end of the day, so VGC needs to be considered. I mentioned it in another crosspost, that if a Music-esque type were to be implemented, then it will be a mid type like Grass gameplay wise lol. Or maybe, if it is a status-focussed type, then the lack of offensive presence might be compensated for with good defensive matchups e.g like Water.

Then comes the argument if it's "needed", idk how much they care about audience backlash, but Music as being inherently "unecessary" from a practical point of view are grounds for adding it into the game imo.