Male or Female isn't an issue or at least it shouldn't be to be a football official.
I don't think we will see mixed teams any time soon though. The best female footballer i have ever seen is Marta Vieira da Silva. Skills wise she is increadibly gifted. On par with any male footballer (honestly she is that good) But what would happen if she is dribbling at full speed against Stoke City on a **** wet night and Robert Huth smashed through the back of her with a two footed studs up brutal challange? Not pretty!