Great theory, except for the fact that very few Christians and Messianics even know what the gospel of the Kingdom is, and it definitely has not been preached for two thousand years now, because of that. Ask ten Christians what the gospel is, and you will get ten different answers. Try it once. Seriously.
Before you ask, I don't have the kind of time on my hands at the moment that is required to explain what the gospel of the Kingdom is in detail. You can answer it for yourself though. Here's how. First and foremost, and this is the most important part, clear everything "Paul" from your mind! Now, if you have a red lettered edition of the synoptic gospels, read the red text only, there is your answer. Jesus, and Paul definitely preached two separate "gospels." I understand it is difficult for a believer in Jesus to ignore Paul's words, but it is absolutely required to know what the gospel of the Kingdom truly is. Also, I will not argue with anyone on this point if they accept what Paul has to say about the gospel of the Kingdom. Actually, I should say "gospels" (plural) because Paul preached several of them. At least everyone in Asia wised up, they must have known the Torah pretty well:
(2Ti 1:15)
You know that everyone in the province of Asia turned away from me, including Phygelus and Ermogenes.
It is amazing how Christians completely miss this verse, or completely ignore it! Don't you think that is a pretty important verse? The founder of Christianity isn't Jesus at all, it's Paul!