>>7770That is perhaps where my knowledge of these things ends. Although, the connotations of Christian rebirth and Buddhist rebirth do have similarities, even if more different than similar. And now that you've brought that up, It's also worth noting the Sri Lankan Protestant Buddhism which sought to westernize Buddhism as a self-defense against the British who saw it as foreign and persecuted it. Perhaps it has something to do with that.
>>7771>Why is Japanese Buddhism so lax?Buddhism came to Japan principally through Tang dynasty China. Tang dynasty China was dominated by an approach to Buddhism that did not take the Vinaya seriously. In Japan, they would develop a strict Mahayana approach to Buddhism that rejected much of what was considered lesser teachings, which included the Vinaya, the rules for monks, seeing them as provisional teachings given by the Shakyamuni Buddha to less competent people. Buddhism in Japan held onto this view while Buddhism elsewhere in Asia moved back towards the Vinaya over time. Combine this with historical periods of persecution against Buddhists and decrees by Emperor Meiji that relaxed rules to the point that drunkenness, marriage, not wearing robes, and long hair was permitted of monks, and you end up with the situation that exists in Japan today regarding the Vinaya. Instead, Japanese Buddhists today generally follow a set of Bodhisattva precepts synthesized from the Brahma Net Sutra. Another major element at play is the Mahayana conception of Upaya, which teaches that even otherwise impermissible actions are permissible if done to help other beings attain enlightenment, even killing a human being.
>I wonder if Buddhists have a concept of possession?It is a thing, but it's broadly a more metaphorical concept than a literal one, especially when Mara is involved. Even in case where it may be literal, as you said, it's really only something that lower order malicious beings (e.g. preta) are capable or willing of. One could take a more heterodox approach to applying the concept of possession in Buddhism, but what that would look like is a bit beyond me.
I kind of hinted at this before, but I do think conjuring up an isekai religion could work in that it could appeal to people who are into new age theology, which is prevalent in America. I'm of course opposed to associating it with Buddhism for obvious reasons. The big road block such a faith would run in to, really, is that it wouldn't be sufficiently secular or new agey for the majority of people who seek out Buddhism in the West. That means that, as a new religious movement in the west, it would really need to appeal to some other established and traditional religious sensibilities (e.g. Christianity, paganism, etc.) or be incredibly culty, and the latter of those is terribly unethical and probably counter to OP's end goal.