This would only work if there was crazy Generals who, if they have an Impetuous trait, are known to just go attacking other armies - especially if there is another trait "Hates Gauls" or what have you.

But in all, it would be frusterating, and you'd need much larger armies to be able to do this. You'd need to have it connected with Loyalty to the General, and it would bring a whole RPG element to it that way as well.