What is he required to have in his command? I assume Bd (O), and also some of all the compulsory troops pro-rated on the Bd, such as Roman Cv (O), Velites/Leves and Triarii?
What if you downgrade some of the Bd (O) to Italian Ax (O)? Could you take some of them in place of the Bd? If so, would it excuse you from having to take the Cv, Ps and Sp?