If you do not follow the historical record and use the forces available, then it is not a historically accurate campaign game
CGs are not meant to be balanced, they are meant to be historical.
This is all nice in theory, but even a CG is still a game. ASL is still not a simulation. Terrain, though more historically accurate, is still abstracted - a lot.
CGs don't list the historical orders for the commander; they define objectives that the players (not commanders - players) will try to achieve. It is the job of the designer to create the objectives so that the players will be led to use their units in a way that looks a little like what a real commander would have done, and so that the players feel a little like real commanders (without the real men dying around them).
But, once the designer has done his job (well, hopefully, but that isn't guaranteed), the CG objectives are really all that exists to lead the players.
But really, what I was trying to say was a bit different. It may be that the historical action that is being depicted by the CG (or any scenario, really) was really hopeless for one of the sides. Many scenarios do that; how the designer is supposed to make the scenario interesting to play is by defining objectives for each side that are not the historical objectives, or the historical outcome, but somehow make the job (roughly) equally hard for each side. So, on the losing side, the defender will try to delay the attacker for long enough; on the winning side, the attacker will try to take the objective terrain quickly, or with minimal losses, or both.
I don't see why a CG would follow different guidelines. The real goal is to have a game (a series of games making up a bigger game) that is both balanced and reasonably historical, in that both players (players - not commanders) will have about 50% chance of meeting their game objectives,
and both should be naturally led to follow historical tactics.
Of course, different players will look for a different degree of each (balance vs "historicity"). But there is no reason at all why a CG should sacrifice balance completely just because it is played on a more historically accurate map.