Conservationist, I get the impression that what you are suggesting is somewhere between a marriage-of-convenience and meta-political entryism. On the one hand, I'm not completely opposed to such an initiative. I'm neither an intransigent nor a dogmatist. The spiritualties of the future will not and cannot be the same as those of the past. Changes will develop, and on a practical level may be made to develop. However, I believe what you are proposing is undesirable for two reasons.
Firslty I believe that in essence the ideologies at the core of Christianity and pre-Christian European religions are incompatable. Christianity is by definition the worship of Christ. The story of Christ, as reported by the apostles, is of a man who submitted, without sturggle or fight, to suffering and death at the hands of his enemy in order to show that our existence is profane and valueless and to allow all people, regardless of their transgressions and/or incompetence, the opportunity to achieve everlasting life as long as they are subservient. Furthermore, Christ was a Jewish reformer, and Judaism, then and now, is monotheist and dualist. This means that our existence is interpreted as an undesirable and sinful tangent to the true being of a beyond which we are incapable of accessing without, again, subservience to His law. I cannot possibly imagine a doctrine further from the heroic/tragic triumphal overcoming-through-struggle that is clearly displayed in traditional European mythology from the Táin to the Iliad. If one were to conjure some form of syncretism between paganism and Christianity one of these central doctrines would eventually have to win out over the other because of their incompatibilty. How do we know this? Because history has shown us so. When Christianity came to Europe it did indeed adopt many pagan practices and aesthetics. Christianity was undoubtedly Europeanised, and I suspect that is what you have been driving at with your 'pagan roots of Xianity' comments. Indeed, the legal and administrative structure of the catholic church, along with many customs and rituals, were lifted directly from pagan Rome (or, more accurately, these structures assimilated the new religion). However, the process of Xianisation in Europe did not stop, and has not stopped. The protestant reformation, quite logically, looked at the bible and found absolutely no foundation for the pope or the catholic church's hierarchical structure or extensive canonical tradition, and consequently binned it all. Today, liberal atheists continue the reformation (albeit unconciously) by removing the 'superstition' of God and all notions of spirituality whilst upholding the core morality and ideology of egalitarianism and the profanity of our existence.
Secondly, there may come a time when an aliance of sorts is required, but this is not it. The interest in pre-Xian Europe and European values has been on the rise for more than a century now, from Nietzsche to de Benoist, from Wagner to Vikernes. Conversely, Christianity is being discredited more and more. Churches are emptying and Christians are increasingly being ridiculed in the media and popular culture. Now, I don't necessarily revel in this, for I have a respect for the religious in general, and a certain disdain for smug atheists, but to side with Xianity would be like boarding a sinking ship - we would go down with it!
Finally, as for your repeated comments about the pagan origins of Xianity, I don't really follow. Jesus was a Jewish reformer, Judaism was monotheist. The apostles basically preached Judaism for gentiles. So I don't agree that Xianity had pagan roots. I do however, as stated above, recognise that Xianity was Europeanised to a large extent after it became the offical religion of Rome, but, as I have also said, many of its most traditional European features have been the subject of reform and excision because of their incompatibility with the central ideology of the gospels.
Erosion, I disagree with you also. The burning of heretics is not burning the weak, it is burning the other because one is incapable of allowing or comprehending difference - difference which is diversity, diversity which is natural. It is indicative of the narrow, totalitarian and completely unrealistic world-view that has caused so much destruction throughout Europe's history. Nor is original sin a recognition that man needs improvement, it is a statement that man is wrong and cannot right himself. It is a statement that man is not fit to govern himself or to be in charge of his own destiny. It is a statement that I disagree with. Strongly.