The prospect of this happening did occur to me when the rules regarding the line of succession was changed, although there are some hereditary titles which cross gender.The Duke of Fife inherited his title from his Aunt for example, and Countess Mountbatten of Burma inherited hers from her father. But this does not go via the eldest and a Special Act had to be put through when such titles came into existence.
On a political level this does not change much. Most Peers eligible to sit in the Lords are Life Peers (meaning their title dies with them) and if the last 100 years are anything to go by the House of Lords will soon have none. However, 100 Lords members hereditary Peers and it is the principle that matters as much as the practice.