There is nothing at all implausible about this scenario. In fact it is far simpler explanation of the evidence than the complex theories conjured up by historicists about "oral traditions" and lost sources. Now, we haven't necessarily proven that Jesus doesn't exist here, but that's not the point. The point is that this explanation for the development of the Gospels is demonstrable with evidence and it is also not accepted by mainstream scholars, despite the fact that it is actually a much more straight forward and plausible explanation of the evidence.