This is one of those ‘hell yeah, that’d be awesome… but not gonna happen’ ideas. For all of the abovementioned reasons and more.
My two cents [size=6pt](and since I’m poor I’ll want them back when you’re done with them, thank you…)[/size] : multiplayer changes the nature of the game.
The idea is not complex; the implications, however, are.
Not quite genre-changing, in my opinion, but certainly a lot more work than reward. After lengthy consideration (a long time ago), I came to the conclusion that making the effort wasn’t worth my time (even though I desperatly wanted to make that effort)… and that if I really wanted to do something like that, it’d probably be better as a mod of another game.
That being said, it is still possible. You’d probably want your ‘players’ to be AI actors whose actions you ‘backseat drive’ rather than control directly (which, of course, takes some of the fun out… and changes the genre and, again, the nature of the game). A major issue, as has been mentioned previously, is the resolution of time as experienced in the game and as experienced by the player. This is a simple problem with a simple solution. We just need to impliment quantum mechanics. I’ll recommend the relevant book as soon as I find it… it’s around here somewhere, but keeps moving when I see it. Supposedly there’s a cat somewhere inside of it. I’ve only really seen the cat’s tail, and that only briefly.
I grant that the unreal engine is one option… [size=6pt]though I’m afraid I preferred the mutilation of minecraft simply because of the existing functionality already present in the code[/size].