That was worth waiting for KoW. Good stuff. I've read others having concluded Daniel 7 was featuring Michael as SM. I follow the logic but have to question the obvious, why not simply make it explicit? Why describe the powerful angelic Prince as 'like a son of man' which has been argued effectively to imply human frailty in Daniel. I follow your logic regarding Joshuah usage of the term, but that was hundreds years distant and likely had different shades of meaning by the time of Dan 7 composition.
Matt 16 famously has Jesus ask who the people say the SM is, implying that their were multiple opinions centered around one of the prophets.
Much like you said: players are tropes borrowed from previous Jewish compositions, stories and writings
The answer insisting the SM and Messiah are one and the same reflects the view of the writer and his community not apparently the majority view even then. The half joking suggestion that the author imagined Daniel to be the SM isn't as crazy as it seems. Like I said the similar books of Enoch elevate Melchizedek, Enoch to godlike status.
I love the suggestion that the Hasmoneans themselves were responsible for Daniel. Maybe, but it would seem easier to assume someone with deep sympathies for their efforts, given the short sighted prediction.