OK, this is what I needed...
Sefer Helachok is speaking to a specific audience, Merkabah mystics. The idea of this angel being a gate or intermediary fits into that context, however, taking it out of that context and putting it into the Moshaich context is a bit of a stretch.
In the earlier Second Temple Enochian and Qumran literature, however - of which the later
Hekhalot literature of the Merkabah mystics represents a development - the human-angelic figure (typically identified or associated in the texts with the Angel of the Lord in Exodus, the one who has YHWH's name in him) that serves as an intermediary of the Divine Presence - usually Enoch or Melchizedek depending on the Jewish sect in question (but also other personages) - was understood as having a Messianic role.
The early Christians picked up this tradition and 'rolled' with it for their presentation of Jesus.
In the
Melchizedek scroll, for example, he is the messianic agent of a future Jubilee salvation. In the ancient exegete's bold interpretation of Isaiah 61:2 (which speaks of “the year of the YHVH’s favor”) the name Melchizedek is substituted for
YHWH (as Enoch-Metatron would later be as well in the
Hekhalot literature). In addition, Melchizedek is said to atone for the sins of the righteous and execute the divine judgment upon the wicked.
In these capacities, Melchizedek is described in the text as: "
the Messiah of the spirit [mashiach haruach] about whom Dan[iel] spoke "...until the time of (the/an) Anointed Prince [mashiach nagid] there will be seven weeks . . . after sixty-two weeks, (the/an) Anointed shall be cut off" Dan 9:25, 26 ... good who announces salv[ation] is the one about whom it is written that [he will send him Isa 61:2-3 "to comfo[rt the afflicted, to watch over the afflicted ones of Zion"]", according to the scholarly reconstructions.
Originally,
Daniel 9:25 (the 'messiah' who is "cut off" i.e. dies) probably referred to the murder of Onias III during the Maccabean Revolt - but for this ancient Jewish exegete writing in circa. 100 BCE, it became a messianic prophecy of the future which he connected with Isaiah 61.
This same kind of tradition is reflected in the contemporary
Similtudes of Enoch where the Daniel passages are used to refer to Enoch-Metatron in a messianic context (thus beginning the tradition where Enoch is the heavenly mediator, rather than Melchizedek, which culminates in the
Hekhalot literature). 1 Enoch reads:
(1 Enoch 46:1) There I saw one who had a head of days,
and his head was like white wool.
And with him was another, whose face was like the
appearance of a man;
And his face was full of graciousness like one of the holy
angels.
(2) And I asked the angel of peace, who went with me and
showed me all the hidden things, about that son of man
—who
he was and whence he was (and) why he went
with the Head of Days.
(3) And he answered me and said to me,
“This is the son of man who has righteousness, and
righteousness dwells with him,
and all the treasuries of what is hidden he will reveal;
For the Lord of Spirits has chosen him, . . .
(1 Enoch 48:2) And in that hour that son of man was
named in the presence of the Lord of Spirits,
and his name, before the Head of Days [God].
(3) Even before the sun and the constellations [of the
zodiac] were created,
[and] before the stars of heaven were made,
his name was named before the Lord of Spirits.
(4) He will be a staff for the righteous,
that they may lean on him and not fall;
He will be the light of the nations,
and he will be a hope for those who grieve in their hearts.
(5) All who dwell on the earth will fall down and worship
before him,
and they will glorify and bless and sing hymns to the name
of the Lord of Spirits.
(6) For this (reason) he was chosen and hidden in his
[God’s] presence,
before the world was created, and [he will remain] before
him forever.
(1 Enoch 62:2) And the Lord of Spirits seated him [the Son
of Man] upon the throne of glory,
and the spirit of righteousness was poured upon him.
And the word of his mouth will slay all the sinners,
And all the unrighteous will perish from his presence.
(3) And there will stand up on that day all the kings and
the mighty
and the exalted and those who possess the land
And they will see and recognize that he sits on the throne
of his glory;
And righteousness is judged in his presence,
And no lying word is spoken in his presence. . . .
and he revealed him to the chosen. . . .
(9) And all the kings and the mighty and the exalted and
those who rule the land will fall on their faces in his
presence;
and they will worship and set their hope on the Son of Man,
and they will supplicate and petition for mercy from him."
Later on in the text, we learn that a biblical personage from the Torah - Enoch - is the eternal Son of Man whose name (according to text) pre-existed with God before the creation of the world:
(1 Enoch 71:13) And that Head of Days came with Michael
and Raphael and Gabriel and Phanuel,
and thousands and tens of thousands of angels without
number.
(14) And he [the angel Michael] came to me and greeted
me with his voice and said to me,
“You [Enoch] are that Son of Man who was born for
righteousness,
and righteousness dwells on you,
and the righteousness of the Head of Days will not forsake
you.”
Whether one puts the 'divine agent' in a Messianic role (as did the earlier Qumran/Similtudes of Enoch) or in a pure intermediary function, the basic fact is that the texts portrary a human being as an angel and manifestation of God (indeed the "
Lesser YHWH") and arguably this is the right context within which to understand the portrayel of Jesus in early Christian texts, such as the Gospel of John.
In this respect, the scholar Peter Schafer writes:
"His [the author of the Similtudes of Enoch's] message was: the highest being alongside God is not one of his well-known angels and archangels but rather an angel who had previously been a man, and this man—as the Messiah—will bring justice and eternal peace to humanity. There is also no doubt that this Son of Man–Enoch of the Similitudes is part of the Jewish repertoire that the New Testament drew on."
(Schafer, p.52 (2020))
There would appear to have been many different and competing understandings of the Messiah in Second Temple Judaism - some Qumran texts posit two Messiahs (a Messiah Aaron and a Messiah Israel), others posit a 'heavenly mediator' Messiah who acts as God's agent and is given the title
Elohim (as with the human-angelic Melchizedek in 11Q13), whilst other texts conform more closely to the ideas that became the mainstream of orthodox Rabbinic Judaism - a purely human messiah with no angelic or divine aspect.
The early Christians emerged from the other strain of Messianism that we find reflected in the some of the Qumran texts in my OP, the 'divine mediation / second power in heaven' aspect of which persisted into the Rabbinic era (shorn of its messianism) in the
Hekhalot literature and caused controversy with the Rabbis in light of its relationship with monotheism, as reflected in the Talmudic references to a "
two powers in heaven" heresy among Jews.
The intellectual history behind these ideas and their transmission is extremely complicated.