Well, I do believe in the existence of heaven, but there are a few discrepancies that don't really fit your theory. For one, God has described himself as the one and only god, and a jealous one at that. He would be by his own admission be unwelcoming to other deities. So while the Taoist view of heaven is perfectly viable on its own, if tried to merge with Christianity it doesn't really make sense.
A second issue is that our God is defined as literally Truth incarnate, among other things. Lying, even for our own sake, is simply something he doesn't do. Not to mention the Bible is full of visions of things that simply don't make sense, and if this were true probably would have been edited a bit.
I am asking because someone in the history actually trying to do that - the Taiping Rebellion 太平天國 in 19th century China. Their name in Chinese literally means "Great peacefully Heaven (on earth)". Though it maybe a bit different than the original religion, like the Mormonism in US, the movement in China created this unusual hybrid, more unusual than Mormonism. But it did in term believing in Bible, but adding one more figure as the founder Hong Xiuquan (洪秀全) believed that in a vision, he is the brother of Jesus. I know it sound weird, but blood/family relationships is the core of Eastern Culture elements. And he intend to build a Christian kingdoms in China, but most people here are Taoism/Buddhism/Confucianism in the first place, its quicker for he to adaptive new doctrines than slowly converting people. And he saw the common elements in Taoism and Christianity believes. If he didn't fail politically, like in history, we might have a new branch of Christian believes. (I am not arguing it's right or wrong, in history believing in Jesus as the son of God in Judaism is also new and unacceptable, and minority believes, as long as it gather enough followers later, it too becomes a center believe doctrine), And I think it should be a constant struggle of keeping old faith, or accepting new possibility that hold a believe system together. You may support it or against it, but they both existed in balanced. However I think most will be against accepting new elements in a mostly converted/culture-stable society, so it can hold its current believers. How many or the degree of acceptance is related with the ratio of non-believers/population. More non-believers around you, more open minded you need to be.
I understand the benefits of incorporating parts of other religions, such as the creation of the Christmas holiday. But that is mostly harmless to the actual doctrine, what the Taiping Rebellion did changed some vital elements of Christianity, and at that point it's not even Christianity. Keep in mind, the apostle Paul actually advocates being like who you are trying to reach (to a certain point) but, for example, saying he is the brother of Jesus is full-on heresy, and more importantly ludicrous. Jesus is God according to our belief, therefore he would have no brothers save for his human brothers, who died long ago.
About truth, I agree for the consistency and maintaining believes it has to be forbidden to lie, in order for followers not questioning the believe itself. (Sorry for the tone sounds a little academic, like observers, since I AM not Christian, not even Westerners) But, do it forbid not telling everything and the whole picture of truth? Like there is a possibility that God as an unimaginable entities such that the whole courts/government of deities in Taoism heaven is just in God's mind/body/entity-self, like the concept of trinity (its defined later, rather than state in the old bible), but multi-entities-unity? And he didn't show it to the followers in the western world is because God can be as many forms as it can be, so he shows in different faces to different people in Eastern world, and the one recorded that, like the people wrote/recorder bible, has to use the concepts of their time to write it down, so it looks outdated/not-make-much-sense to us now. It's the fault of us humans that they are recoded differently. Like in a scenario there are many Abraham/prophets not recorded in ancient land of China, or did recorded but due to language difference/distances, so didn't incorporate their vision of God into current version of Bible (chapters are collected and selected in Rome-era churches, many are discards, and I don't believe even they have the scrolls, written about God from prophets in Chinese, they would understand the language, let along accept it). So the memory of Gods show itself to different prophets in different faces, granting different prayers, are viewed by the rest as many deities from heaven - like in Taoism. Anyone told any lies? No, and perhaps not even faults (not intentionally), but just restricted by the limitations of human themselves (in traveling, knowledge, comprehensions, languages, even our short lived lifespan), you can't blame those forerunners/prophets really. So why can't they be both telling a different perspective of a single truth as you have faith in it? Or is this point of view, will be seen by you as devil's advocate to you?
Well, if I understand what you're saying I can't really say for certain if that's even true. In my copy of Genesis God refers to himself as a "we". This may be something done by newer translations and not be present in the old texts mind you, but if it's true it would set a precedent for the trinity. Why he would reveal the trinity later and still yet withhold the other potential parts of him makes little sense to me. Not to mention one must question what exactly the point of them would be. The trinity is clearly defined in its roles (as clearly defined as a god can be, anyway). The Father is the ruler, the Son is the voice and the savior, and the Holy Spirit is the part of God that resides within us all, according to Christian doctrine. What roles are left for any other "parts" to fill?
And I think the second part of this is referring to general revelation. The idea that in parts of the world where Christianity could not reach, the message of God is spread to people in similar forms, and worship of that is accounted as worship of him. It's a real recognized thing, and there's much debate over its credibility, and I'm not sure if it applies here. I don't actually know a whole lot about Taoism to be honest, so I can't say for certain how compatible the religion as a whole is with Christianity.