While I am not as of yet online at an ACMI it has been my experience from speaking with people who work at multiple ACMIs that offer home basing that "officially" (per the contract) it is not an option. However, they will "work" with you to a certain extent provided it benefits the company (cheaper) and doesn't infringe on the schedule. Other options typically include getting positive space on a company flight to a location near to your overseas home from which you would personally be able to purchase a cheaper ticket as well. Each operator is different as to the degree of "workability".