Yes, doing things backwards is not a simple thing. There is no law that prevents it but it means an awful lot of code and I figure Eugen considered it just not worth the effort for such a rather minor feature. It's hard to explain it though, if you don't have a programming background. But if you did, you wouldn't ask, of course. Just remember that you're not watching a video there; reversing that would be easy. But all of the effects would have to be done again and that's quite hard. To illustrate this, let me give you an example that's probably more easily understandable:
At minute 1:00, the replay says an artillery fires a shot somewhere. In this action it's already said where exactly the shot will go and how much damage it will deal when it lands. The replay keeps this in mind and at minute 1:10, it knows that the shot touches the ground now and simulates the damage to everything that's there. Now, let us assume you would want to rewind this. The game now turns to minute 1:10 and we know that the artillery shot fired in minute 1:00 should hit something here. But the information for that is all saved at the point of minute 1:00, not minute 1:10. So the game would have to take into account all the actions that were initiated before the point where it is right now as well, including maybe an order for an infantry unit to move somewhere (and still moving) like 5 minutes ago. All of this would have to be circumvented somehow and believe me, I've only scratched the surface here. Simulating a battle forward is much easier though because it means running the same battle engine that is used in real battles and just entering the commands from memory instead of letting the players do it.
The ability to go back a minute or two would also mean saving a certain state; if there is no way to save a game (and I don't think there is) this would have to be implemented as well. It would mean turning temporarily held variables into a consistent state. Save games have to be compressed; Wargame takes a few Gigabytes of RAM and quite a bit of this is used to save the state of a running match in an easily and quickly accessible form (so the game can run smoothly) which is on the other side very storage-intensive. In order to create a save game this would all have to be broken down from a few hundred Megabytes to just less than ten. Having a real recording would make replays incredibly huge and is simply not feasible. You'd probably have to delete your replays if you had more than ten just because you'd run out of space and I don't think that's worth it for everyone just so they could rewind a replay although I know it's a bit annoying if you missed something at minute 50:00 and you would like to see it again.
If saving a game is not an easily viable action then going back to a certain point would mean simulating all the actions of the match (because that's what's saved in the replay) all over again from the start up to that point. And I know that when I go to speed 10x it still doesn't run faster than like 8 times or so, so it would take quite a lot of time for a normal computer to do that.
I hope I could help you a bit with that.
