Historically, in just about every pitched battle, each side has some kind of Reserve in place that the general can then throw into the battle where he needs them.
My wargaming friends and I are going to start prepping a separate 250-point (or 500-point) "Reserve" list for each battle, with the idea that it can't come into play until at least the 3rd turn.
We're trying to work up cool rules for how these Reserves would function. Here's what we've got so far:
1.) Unlike normal reinforcements, a Reserve force should be able to enter right at the start of the Movement Phase, and even declare a Charge if there's an enemy within range. When it does enter, it starts with its back against the table edge but then functions just as if it had been there all along (which makes sense, since it would have been watching the battle in front of it, awaiting orders to enter the fray). This means it can move as normal, charge as normal, march as normal, shoot as normal, etc.
2.) The Reserve must contain a full command and must be "bunkered" either in the center or to either flank — not on the table, but declared in one of those positions at the start of the 2nd turn. (Each player would write down on a piece of paper where their Reserve is positioned, and flip it over when it comes time to send in the Reserve.) The idea here would be that the General should be able to see the battle begin to unfold before sending word to his Reserve on where to align themselves behind his lines.
3.) It's gotta make sense for it to be able to actually reach something to fight for it to be sent in. So in order for the Reserve to enter the battle, there must be an enemy within 48 inches of where it would enter the table if it enters at Turn 3, an enemy within 36 inches if it enters Turn 4, an enemy within 24 inches if it enters Turn 5, and an enemy within 12 inches if it enters Turn 6.
4.) The enemy should reasonably be able to spy out a massed reserve in the distance, so they would know if they were infantry or cavalry for instance, but they wouldn't know much more about them than that. To reflect this, the players wouldn't have to reveal their Reserve list (including any special characters or magic items its carrying), only the kind of troop and the size (in points). Other than that, it remains something of a mystery until it hits the field.
Does that sound workable? Any suggestions on improving it?