Fizzer: "WarLight used to have this feature. However, after testing it, we found it really wasn't fun. So it was removed and replaced with the multi-attack that we have now.
If you dig around you can find some old games that used it. The problem is it allows infinite amount of delay since you can just transfer armies back and forth forever. If it was ever brought back, there'd have to be some sort of limit instated. "