Titles that the King could remove he did, and there was a bit of a fudge over the Dukedom, as the government didn't want to allocate time to it.
Recently it looked like they might do it for Mandelson, so I wondered if they would word it such that it would include Royal dukes as well, but I think they've abandoned it again.
The line of succession change is interesting. It takes approval of 15 commonwealth realms, and there are different mechanisms in each. According to one historian I was reading, in 2011(?) when they wanted to change the letters patent to remove male preference (sorry can't remember official terminology) it took 11 months, and restarted discussions about reparations.