50-50 vs physical custody?

Does anyone know if 50-50 custody versus primary physical custody can be based on conducive schedules to the child? For example if one parent is shiftwork, random weekend work, up for changes, possible on-call and the other parent is a teacher with holidays, weekends, summers off. The daycare that our child is in is actually based off of teacher schedule so she closes when school is out. My soon to be ex is refusing to negotiate on 50-50. He says that it does not matter that my schedule is conducive to her schedule and that yes I will have her during breaks, holidays, and the summer but we will sort that out in scheduling but that I do not get primary physical custody. Does anyone have any insight as far as their own experience or if you are an attorney in Virginia?