This idea has some interesting potential, but there are also a lot of mental red-flags coming up. In short your idea runs the risk of being too cliched, but if those cliches can be either avoided or embraced, the game would be a lot of fun to read.
Firstly the open and closed Heaven/Hell, Good/Evil dichotomy is stale, even subverting it is stale, so you need to go deeper. You should be using both sides in your ‘war’ to explore some deeper issues, rather than just saying “Yeah the Angels are Lawful Good, but are Devils Lawful Evil or just insanely cool misunderstood loners?”
So go back to basics, and maybe grab a few moral philosophies textbooks to skim through as you go.
First off, try to determine why your two sides exist. That point seems self-explanatory, right? Wrong. The notion of God and the Devil is actually a tricky one, biblically the two aren’t often described as enemies so much as two friends having moral conversations and using Mankind as examples or test subjects to prove their points.
These texts can show a nuanced, even friendly relationship between God and his supposed ‘enemy’, meaning most of the firebrand rhetoric about an eternal war between heaven and hell seems like a massive oversimplification.
I’m not a religious scholar (or even particularly religious), but I’d rather read a story about the nuance and insight of those two moral thinkers rather than a hackneyed White-Knights versus Goat-Legged Sex Monsters or one of those awful YA novel-type things where the scary monster is actually a sweet vegetarian homebody with sick abs and a thing for bland, nondescript teenage girls.
So establish the moral stance of your angels and your devils, and then use that platform to ask the reader who is working in Mankind’s best interests?
The ‘Angels’ will likely found their society and principles on the notion that a sin is always a sin, right? When you steal, you’re always committing a sin, even if it’s a loaf of bread to feed your family, right?
The ‘Devils’ on the other hand might believe more in individual determination, the notion that you personally decide what is right and what is wrong, and then strive to live to that personal moral code. It’s a more flexible way of living but no less valid than the Angels’ views, right?
So their ‘war’ is for the Hearts and Minds of Man, rather than territory or plunder. The whole meat of the game is the moral question of who is in the right, so don’t half-ass it. Choicescript is not a good way to show off action games, so do not believe for even a moment that readers are interested in big set-piece battles. They are not. They cannot see said battles taking place.
I would love to write about 200 pages about this particular subject, so instead I’ll just throw down some bullet-points to get the jist out there.
Don’t have God or the Devil be an actual, physical character in your story. They will never be impressive enough or interesting enough to justify their inclusion. The whole mystery and power of a deity is completely stripped away when somebody tries to add characterization to them. In Dogma, how many words did God say? That’s the exact number of words he/she should say in your story.
Have you ever considered how monumentally strange is the mind of a being able to create our universe? How baffling and labyrinthine its thought processes? How petty our every word and thought must be when placed next to one so far above us as we are above E-Coli? Think about it, and when you’re done thinking about it, read some H.P. Lovecraft. A God is a being so far above us that even to look upon him is to receive a sensory overload guaranteed to break your fragile human mind, so don’t just put Morgan Freeman in a white suit and call it a day.
When contrasting Heaven and Hell, make sure that you don’t draw a conclusion and accidentally write it into the story. Let readers argue and debate which side is correct, make the arguments for each side so compelling that nobody can conclusively come down on one side or the other. You can have your personal opinion, but this is a game/story that is all about choice, so let your players/readers have it.
I have more, but I don’t wish to take up too much of your time. If you want to talk more about this sort of thing, or would like somebody to bounce ideas off of, please feel free to PM me, and I will be happy to help.