If the partner is futa, move the sexuality to middle? That could work. A futa is certainly more feminine than masculine.
Also, balless futas do not trigger the cum actions (partenr wishes to taste cum, if you cum in mount, it's not registered). It appears as they do not produce cum at all. Why not simply make the "balless" futa have internal balls? Code-wise, the only difference between a balless futa and a futa with balls would be the description.