No, I don't know "Thinking Allowed." Grof is always interesting though.
I called your writings 'resonant' because they seemed to support the mystical view of reality. Is that a misreading of them?
I've been thinking about this universal religion question and decided that I was coming at it from the wrong angle.
If a universal religion is based on an unverifiable doctrine then it will never be universal, since many people will not join it, not having any faith in that doctrine. So showing the doctrines of the various religions to have a common root will not be enough. People can still opt out.
The only possible universal religion then is one whose doctrine is verifiable by anyone. This entails that the doctrine of this religion be true, describes what is the case, for rather obviously one cannot verify the truth of a false doctrine. As there is, presumably, only one completely true cosmological doctrine, then this universal religion would have to be founded on this doctrine. So a universal religion would have to have a true doctrine that is verifiable by anybody.
This entails that any universal religion must be methodologically based on mysticism, on contemplation and meditative practice, on first-person experience, since no scientific or metaphysical theory can be verified as being true. True and certain knowledge can only be knowledge by identity, as even Aristotle concluded.
In this religion 'mystical' practice, the exploration of ones own consciousness, would have to allow the truth to be verified by anyone with the time and patience. But for others the possibility of this verification would have to be taken on faith, just as a blind man would have to take the laws of optics on faith, to use William James's example.
Of course, those who had only faith would tend to have their own views and conjectures as to the truth, since they would not know it. Then no doubt some of the more charismatic and opinionated of those who have not verified the truth would start their own various religions with theoretical and conjectural doctrines that are not the truth, and others who also hadn't got around to verifying the truth might become members rather than bothering to check on the truth. Then we'd end up where we are now, with all mystics agreeing on the truth and its complete verifiability, incuding the all founders of the world's main religions, and all others believing in some variation or other rather than checking the facts for themself.
So I don't think we can have a universal religion until at least a majority of people have verified what is true, and maybe not until everyone has done it. But if everyone has done it then we won't need a religion at all, as mystics argue. So even then we wouldn't have a universal religion, just a universal agreement.
So no, I don't think a universal religion is possible, since to be universal it would have to cease being a religion and become simply a shared knowledge.