Good post. The history of the monk, and your takeaways of its design tropes from that history, seem pretty spot on to me. Probably my only point there is that I feel the monk has always had a secondary trope of carrying a bit of divine flavor; obviously it's origin as a cleric subclass in OD&D, but also unarmed fighting kits for clerics in 2e, and prestige classes favoring monk/cleric and monk/paladin combinations in 3e. That seems to mostly have gone away by 5e, with the psionic monk being a precursor of that flavor change when it was introduced in 4e.
I think your playtest observations are pretty on-point. I understand and support the impulse to have both unarmed and weapon-based monks as valid tropes that the playtest is following. But they need to be explicit as to if unarmed strikes are going to have magical item support. I don't feel that 5e's current "do what you want" magic item approach makes balancing intra-class specialties (like unarmed versus weapon-based monks, or Str vs Dex fighters) truly feasible within the rules; the DM needing to add weight to the scales somewhere seems like a near necessity if build balance is at all a play priority.
I would say that Monk Stunning Strike does give benefit to the Monk; assuming a Monk uses and succeeds on their SS use, they'll still be able to make 3 more attacks that turn benefiting from the Stunned condition (if their Di points hold out). Allowing the stun to extend to the end of a monk's next turn would give 7 attacks on a stunned target, which might be a bit too strong. (Although reasonable people can argue about the overall strength.)
I can understand why they choose to move a lot of the weird, wacky Monk flavor ribbon out of the base class, but I would like to see them moved into specific subclasses that support those ribbons. Weird immunities, strange movement abilities, and supernatural perceptive abilities should all be in the Monk's wheelhouse.I