I like the idea, however "wall" (according to the standard game system) is valued less than attack, so to be balanced, I'd say maybe.
Attack 0, Charge 7.
And it's just a matter of opinion, but I don't like the name flavorwise, though I get that you're relating it to simple wall. (Also to be the exact soldier equivalent of simple wall, it'd be: "If opponent's wall > 0, Attack 3, else, Charge 10 or Attack 10.")