But this is apparently the kind of problem that *can* be solved for a computer game if you throw enough processing power at it. Check out this Ars Technica review of Achron, an indie game that has been in development for an astoundingly long time and has finally hit alpha. It sounds exceedingly neat: basically a real-time strategy game with time travel, so you can go back and change past events, and have the consequences ripple forward to "now".
The review describes the game as relatively simple, but I suspect that that's a good thing -- if you're going to toss the fourth dimension into a game, it's likely a good idea to simplify the ordinary stuff so that the player's brain doesn't explode. Overall, it sounds extremely neat: really, the first RTS in many years that's actually got me curious enough that I might check it out sometime...