If we're going for equality between the sexes, why should the wife of the Prince of Wales lose her own identity on marriage and take on his style and title? Husband and wife are no longer one person in the eyes of the law, so they should have separate styles and titles.
The Prince of Wales' wife could be made a Princess in her own right. In William and Kate's case they could be called TRHs Prince William, The Prince of Wales, and Princess Catherine. Likewise, if their firstborn is a girl named Diana, her future husband would be made a Prince in his own right and they could become, in due course, TRHs Princess Diana, The Princess of Wales, and Prince (first name). This proposition also provides for the couples to eventually be HM King William and HRH Princess Catherine and HM Queen Diana and HRH Prince (first name) respectively. Perhaps the consort could have the style of "Majesty" rather than "Royal Highness" to distinguish them.
Radical, but more in line with modern trends towards equality of the sexes.