The matter of women deacons is in a different state in the Catholic Church from that of women priests. Pope John Paul II stated that it was not possible for women to be ordained as priests. His argument was that Jesus had chosen only men for the 12 apostles, and that the apostles did the same when they chose who would succeed them in ministry. He also made use of the “in persona Christi” image which you cite in your question. John Paul II went so far as to indicate that Catholics should not even discuss the ordination of women to the priesthood as a possibility.
Women as deacons is another matter. It is still open to study and discussion. There is some evidence that women served as deacons in the early Church. For example, St. Paul speaks describes Phoebe, as a “deaconess” (Jerusalem Bible) or “minister” (New America Bible) of her local Church (Romans 16:1). The “Apostolic Constitutions”, a fourth century document, describes a ceremony for ordaining women as deacons. The service for the ordination of women deacons involved the laying on of hands by a bishop and an invocation of the Holy Spirit. There appears enough evidence for a Scriptural and historical precedent that further study is indicated.
Such study could lead to the revival of the order of deacons for women. The order of deacon as a permanent ministry for men had nearly vanished in the Church prior to the second Vatican Council, becoming not a distinct ministry but a stepping stone (sometimes for only a day or two) on the road to ordination as a priest. In recent years the role of deacon has been revived for men in a way that builds upon its function in the early Church. It’s certainly possible that something similiar could happen with women deacons at some future period.
I hope this helps answer your question,