I think that the Power of the Keys, that you mention, is the crux of this issue.  The power to bind and loose in earth and heaven, suggests that Church is free to define its story, to develop ritual, and a culture that supports the Proclamation of the Gospel.  If a female priesthood is necessary to the effective proclamation of the Gospel in the concrete situation of our present world,  then the Church is free to ordain women to that priesthood.