In a game of perfect information, without idiot rules to contain the French player, and given the actual forces present, the French should have no difficulty at least successfully forcing a passage to Verdun if not smashing a large part of the German in detail.
That is why I am looking at the full French and German OOBs. My picture of a game for Mars-la-Tour begins with establishing, for each side, the forces and mission. The players will have some pre-battle process to established what forces the have, and distinguish which stands represent troops actually present. For a fast club game, the gamer presenting the game will probably set this up in advance; or it could be a question of rosters selected at random.
It would be relatively easy, for example, to program an excel spreadsheet to pump out half-a-dozen candidate OOBs and objectives, with the player selecting from his options; or a smaller set of complementary options. An example of a generalized form of this is Novak and Chadwick's Road to Glory system from the latest version of Volley and Bayonet.
In an ideal world, both sides should be chuckling about how they will "pull one over" on their opponents.