I don't think the GOAA requires celebate deacons or priests to be monks, in order to be ordained to the episcopacy. Metropolitan Gerasimos was the Archdeacon to the Archbishop of America, held an administrative position with Holy Cross School of Theology, and had a private psychiatric practice, prior to his episcopal ordination. (Metropolitan Methodios of Boston was the Archdeacon to the Archbishop of America prior to his priestly ordination, was very promptly---the next day as I recall, set apart as an Archimandrite, served a parish in New York for a time, and was later elevated to the episcopacy, and named Bishop of Boston. Metropolitan Evangelos of New Jersey, had been a Deacon assigned to the Archbishop of America, and was later ordained a priest, served as a parish(es) priest, and then was elevated to the episcopacy, directly for the New Jersey Metropolis. Metropolitan Nicholas of Detroit, when he was ordained a priest, served as Chancellor of the Diocese of Pittsburgh, later transferred to the Archdiocese in New York, before his episcopal ordination for the Detroit Metropolis. Metropolitan Maximos of Pittsburgh is a monk, though he had been Holy Cross' Assistant Dean, and concurrently served a small parish, part-time He was a Great Archimandrite. Bishop Savas of Troas, an auxiliary to Archbishop Demetrios, was a parish priest, the Chancellor of the Holy Archdiocese--became an assistant bishop while he was chancellor, and now serves as the Director of the Archdiocesan Church and Society Department.)
I think, though, as Fr. Anastasios noted above, the tradition of the church is to select episcopal candidates from among the monastics, who had lived and were immersed in the angelic life, as preparation for episcopal service.