Greetings Leolaia.
That is an interesting alternative approach to the passage. I dare say, I have not encountered it before.
I struggle with your comment that Jesus used "Son of Man" to refer to humanity in general instead of to Himself specifically. Of the approximately 80 times Jesus uses the term in the gospels, I have found that each one is a direct reference to Himself. Such self-references include when He refers to Himself as judge over the earth, or coming in His glory, or having authority to forgive sins.
To be a credible alternative interpretation (i.e. that all humanity is the real lord of the Sabbath) it would be necessary to show that Jesus at least sometimes used "Son of Man" to refer to humanity in general instead of to Himself. I am unaware of even a single such usage by Jesus, much less an habitual one.
Further, you state that Jesus borrowed the expression "Son of Man" from the extra-biblical text 1 Enoch. While I understand your enthusiasm for ancient literature, the assertion betrays a bias that an historical Jew, such as Jesus, could not have shared. If Jesus was an historical man, and if He was the "Son of God" as He claimed, then He would have more likely borrowed the "Son of Man" reference from Daniel 7:13-14. In fact, Jesus quoted Daniel 7 during His trial in reply to the question, "Tell us if you are the Christ" to demonstrate that He did consider Himself to be the "Son of Man" coming in the clouds to reign over an everlasting dominion (read Matthew 26:63-65). As a result of Jesus' quotation from Daniel 7 the leaders were able to decree that Jesus had blasphemed.
Finally, in considering the context of the discussion about the lawful actions on the Sabbath, Jesus mentioned that "something greater than the temple" was present. Just as He had done with claiming that His glory was greater than that of Abraham's (read John 8) He now claimed to be greater than the temple. It seems out of place to think that Jesus would first claim to be greater than the temple and then suddenly tell the crowd that all of them were the true lords of the Sabbath. It is more likely that Jesus was citing His credentials and authority (as Lord of the Sabbath) to demonstrate that His interpretation of the Law of the Sabbath was superior to that of the Pharisees.
In all three synoptic gospel accounts of the story, after Jesus claims to be Lord of the Sabbath and subsequently heals people in defiance of the Jewish officials, the officials are recorded as deciding to find a way to have Him killed. Did they really desire to kill Him because He could heal people, or did they want to kill Him because He claimed equality with YHWH when He called Himself Lord of the Sabbath, a claim to higher authority than the officials possessed?
Thanks for the discussion, Leolaia.