My "plan A" of attack is based on the model used by a number of "Copenhagen School" names who posit that much of the Pentateuch narrative was inspired by (created to meet a need for) new settlers in the land of Canaan at the time of the Persian conquest. The new inhabitants were brought by Persians to Canaan from Mesopotamia, and others came up from Egypt, to form the colony of Jehud. As was done elsewhere with mass migrations (forced) new ideologies and/or gods were created to justify the move and give the new inhabitants a new identity in their new land and (often) among native inhabitants with different language and customs.
I sometimes have wondered what would happen if we apply a similar type of model to the gospels. Would it work? Of course the above model is a thesis that derives from applying the standard techniques of historical inquiry I have set out at the beginning, at the OP here. So my interest is to work within those "rules" for the gospels, too.
The model used by some members of "Copenhagen School" is certainly not primary, or even secondary evidence, nor something widely accepted by critical scholars or historians investigating the same topic. I do not think these scholars of the "Copenhagen School" used evidence for their conclusions (as you described them) which was primary. And then they do not agree with each other and their works were deemed controversial.
And if you got inspired by that model in order to study the gospels, I think it is a bad start. Also, I do not see how this model is a thesis that derives from applying the standard techniques of historical inquiry you have set out at the beginning, at the OP here. I do not see any connection.
One suggestion (not mine) is that the Passion Narrative in Mark, with its ironic (anti-)imperial themes and focus on crucifixion as a potential fate of all steadfast followers of Jesus, addresses the situation of the masses of crucifixions outside Jerusalem in 70 CE. A related suggestion (again not mine) is that the midrash of the empty tomb points to the Isaianic prophecy of the destruction of the Jerusalem temple.
Oh, your perceived irony becomes a criteria.
"focus on crucifixion as a potential fate of all steadfast followers of Jesus," is a wild speculation.
"addresses the situation of the masses of crucifixions outside Jerusalem in 70 CE." ditto, that's even worse.
"the midrash of the empty tomb points to the Isaianic prophecy of the destruction of the Jerusalem temple."
Oh, what's that?
But the gospel is about more than the crucifixion. One other theme is that of persecution of the followers of Jesus, and it is difficult to find evidence for that situation around 70 CE. Some have pointed to the 90s as the earliest evidence we have of persecution of Christians. I think the evidence for that is slight, however. It is based on the Jewish synagogue curse against heretics but the evidence that these heretics were Christians is not strong, iiuc.
The evidence for persecution before 70 CE is in Tacitus & Suetonius' works, and Paul's Galatians 1. And also in Acts. Why look further? But of course you reject all that evidence.
Return to Paul's letters: he speaks of being a persecutor and being persecuted. Perhaps we need to be interpreting "persecution" in Mark through the somewhat "relatively mild" form persecution took in the case of Paul.
Not so mild: look at Mark 13:12 "Now the brother shall betray the brother to death, and the father the son; and children shall rise up against their parents, and shall cause them to be put to death."
(I ignore the late fiction of Acts, of course.)
Assumption again: Acts is all fiction!
What is the Gospel of Mark?
What do some of the stronger literary analyses of the gospel say about it? One that I think is a recurring observation is that the gospel's narrative is nested in themes of the Second Exodus (i.e. Isaiah especially).
Another wild speculation, and far-fetched at that.