I never went through with it though because the story I had in mind would maybe have taken about a thousand hours for one person to implement.
It's not just the story but the amount of effort that would've needed to have gone into laying out the game's philosophy as well. Things like journals/diaries, books, etc would have to be written, diagrams drawn and updated in game, memories and flashbacks created, etc.. The most important thing needed to tie it up was a set of chapters written by two key historical figures from an older civilisation; one of whom was highly influential, if not entirely responsible for a revolution in thought, whilst the other was an obsessive and insecure thinker who feared the truths of those findings. That bit alone would've taken hours and the idea was to subtly hint that the latter was the previous human form of the main antagonist, and that he ended up as he did trying to reject the nature of existence. This guy eventually became something more akin to a being like Sin from FFX, and was sealed up during a huge war between himself and that civilisation (at the cost of the majority of their lives).
I'd loved to have made it but it just wasn't realistic when you combine that with the actual gameplay. One of the characters in particular would've taken an age to write - I needed to write in a false surface character development that would've come off as something of an existential crisis (given the sorts of things the group start experiencing), where as in reality it would've been turmoil resultant from the impossibility of his deceit. He was to be written as part of a separate group of individuals (sort of like apostles that were produced by that Sin-like creature) that had previously raised the main character for a large part of his childhood, having already identified him as a reincarnation from that older, lost civilisation, and someone that could eventually release the antagonist from the shackles that were put on him during that era. That group captured the main character at an early age and began to enforce torture and other methods to stop him from developing into the being he was destined to become, whilst also crafting him so as to be able to manipulate him into freeing the antagonist. Long story short...he escaped, was seized by a section of the military, and the deceitful character is given the job of bringing him back in. The whole thing becomes a complete disaster though due to the other people that enter the equation, with him eventually having to befriend them and craftily steer the group towards their demise (too much effort to explain why he was the only person to be able to do this at this point!). One of the key parts of this is the constant undermining of another character whose outlook on life is uncannily similar to that of the lost civilisation's, and as such is a threat to the group's purpose of using the main character to free this Sin-like being (without triggering his potential). The dialogue between these two characters would be quite similar at times to that of an argument between a conspiracy theorist and a sceptic, with the deceitful character ridiculing the other character's beliefs and steering the main character away from that line of thought. It doesn't work, and the deceitful character is reduced to panic and dread as he watches him slowly turn into what these apostle type people were trying to steer him away from becoming.
There are so many other plotlines and agendas that sandwich around all this (the whole thing for example is done in context of a hidden war occurring either side of something called the 'dimensional veil', and it is a 'war' in the sense that there are two opposing sides trying to steer earth and these characters towards different realities), and I didn't really know how to approach the issue of the soundtrack either. I am definitely no musician and would've been reliant on someone else scoring it, but even if that happened I'm not sure what atmosphere would fit. It would needed to have been more Jeremy Soule than Uematsu, but then that wouldn't have been appropriate for some of the more shocking in-game twists. Dumbing down the philosophy and the dialogue was the only thing I could think of, but then that was what I liked most about the idea.