I think an unstated problem within this thread is that you need to come up with a huge amount of editing within a fairly short period of time - and then have the multiple results to be considered authoritative (mostly) by the early second century.
In addition, it is difficult for me to ignore what appears to be a sort of crafting that others have spoken about: Mark looks like it was written for Romans, Matthew for Jews, Luke for Greeks and John for mystics. I also think that John needs to be written last as its viewpoint looks VERY Gnostic ( or proto-Gnostic?) and otherwise distant from the original events in Palestine, as in the way it refers to "the Jews" collectively.
There is a philosophical defect in these analyses, I believe. On the one hand, scholars take a 'naturalist' approach in which the Gospels must be dated after 70 AD on the presumption that prophecy is impossible. In contrast, the faithful accept it all as history and date them much earlier.
As with evolution vs creation, it is difficult to create a 'middle' viewpoint, in society at large!
I can't see Matthew as a clever fake, as Ray Franz's arguments still hold water. If editing or collusion is true, they should have fixed or cleaned up a lot of apparent errors and that goes for the other Gospels as well.
Contrarywise, Leolaia makes a solid point about the Gospels as 'midrashim'. The Watchtower, in particular, keeps asserting this fallacy that ancient people thought or spoke about their world in the same way that we do today. We are deeply influenced by a technological and legalistic culture that these folks didn't have. This is also why ancient languages fall by the wayside and why one Japanese researcher told his comrades that their results needed to be communicated in English. Their traditional tongue was not exact enough.
In the end, you also have the apparent fact that, for quite awhile, the written Gospels were superfluous because Christian churches had multiple living witnesses to Jesus' being alive after his execution, as Paul notes.
And you thought the solution was easy?
metatron