“This would involve moving the four Gospels to the OT.” This would be okay. The divisions, paragraphs, punctuation, naming, etc is all something that was added long after the text was given. Calvin put the book of James at the end of his Bible because he didn’t like it. I don’t recommend that, but I see no problem in what you are suggesting. Perhaps the gospels are in the NT because they are “gospels” or “good news” and that certianly is what Jesus came to bring. Also, how could you understand the New Covenant – with out understanding Jesus? Either way..but I would leave it as is.