|"I have given you an example: as I have done, so you must do."|
As Pope, Francis effectively changed the rubrics on his first Holy Thursday; now he just made it official. I am not a big fan of women getting their feet washed (and certainly wanted to have nothing to do with it while the rubrical restrictions were in place), but my resistance is mainly from a sense of distaste at all it involves in terms of hosiery (not that ordinary women wear hose anymore).
This is a departure from the 1955 rite (which restored an extinct practice), and from the earlier customs. It is safe to say that the medieval and earlier foot-washings involved men alone simply out of reasons of decorum. Other ceremonial (but non-liturgical) foot-washings with women were carried out by women. Either way, participants were often chosen from the poor, offering exactly the sign that the Pope hopes the revised rite will help manifest: the "limitless charity" of the one who loved us and gave himself up for us.
We may have gotten used to the visual of "twelve men/boys" representing the Apostles, but the washing of the feet was less about the priestly character of the Apostles than it was a graphic exhortation to service on the part of those who represent Christ--just as it was on that Holy Thursday night.