Rabbi Ovadia Yosef did not say that women may wear trousers. He allowed a small group of girls to wear trousers temporarily until the girls could find longer, modest skirts to wear-a matter of days.
Takanas Ezra said that women must wear underwear under their skirts just as men do.
Yad Haketana – as quoted in the Darkei Teshuvah 9, and Divrei Chaim vol. 2 s. 62. , also Yabi’a Omer ( this by Rabbi Ovadia Yosef ) ibid – also – NO trousers to be worn by women.
Once again there is nothing lovely in trousers for women, whether brand new , or colorful or old or torn.