@ Sir Malic
I am impressed by your analysis and diligence to dig the historicity of the gospels (synoptic gospels more specifically). And I would like to note the part where you stated Mark was used by Luke and Matthew.
THIS IS CORRECT.
Mark precedes all the other gospels by virtue of antiquity. If scholars would have it, Mark should have come first in the Gospels rather than Matthew.
It is WRONG to believe that Luke and Matthew WERE EYEWITNESSES nor the writing of their gospels were culled from direct eyewitnesses themselves as claimed by one of the posters here (pardon his ignorance).
Quite interestingly, had the
Q Documents (which by the way also precedes Mark) been extant or available during its compilation there would have been four synoptic gospels today where the Q Documents would have been the "master manuscript" of them all. Or... it is also possible that there would have been only two gospels today if that Q Document was found -
The Q manuscript (setting aside Mark Matthew and Luke as extra biblical reference) and
John. Or...still three gospels but only the Q Manuscript, Mark and John (setting aside Matthew and Luke again as extra biblical reference).
I am not sure though if the gospels Matthew and Luke were penned purposely to deify Christ but the Q documents would have been one of the critical answers to your questions. In the absence of a conclusive evidence, I think it is too early to declare that the Gospels of Matthew and Luke are "alterations" of the Markan gospel.
It is a good theory nonetheless.