From: The Great White North!
It seems to me that if there is a leadership check required in the defence - which allows the reserve to be committed to fill the gap; it would follow that the opposite should be true if an attacker wishes to pursue. The check should probably include issues like supply, fatigue, preparation points, command, leadership and experience. If each side has to make a check, the player who plans better should (in most cases) win the draw if both the defender and the attacker have to make a check at the same critical point in the battle. Otherwise, the attacker has an unfair advantage - the defender does a check but the attacker always launches the reserve (without a check).
The question of an armoured or an infantry reserve being better could be debated. To me, its terrain dependant, an armoured reserve is better in clear, open or lightly urbanized, infantry better in jungle, mountainous or heavily urbanized. In general however, armoured or to a large extent mechanized reserves are more able to react quickly - and thus are more responsive to a command decision to pursue than a pure infantry formation normaly would be, and could move faster to seize tactical advantage.
I know that this is way too late for initial release but it may be worthy of further consideration for a later patch. I think that both sides should have to go through a check routine, and that routine should benefit the side with forces better supplied, trained, rested, prepared, commanded and led. When all the variables are compared it should make for some very interesting (and probably more historical) results. It may allow a skilful defender to 'break clean' from an attacking force in order to re-establish the defence, or if the defender's check failed and the attacker's succeeded the defence could be unhinged. Perhaps if they both succeed, either a stalemate or a secondary meeting engagement ensue. Not sure of the mechanics, but in a game where we watch individual fighters launch to join CAP defence, the launching of a Brigade or Divisional size reserve element should have a bit more consideration.
Have seen some concern in other threads over the need to slow down the tempo of the game. Checks such as this may do that for land combat.
Just my $0.02 worth. Looking forward to the game - the work you guys have done is impressive.
Can't remember which went first...