I was looking up vacant dukedoms and Sussex seemed the best or better than most available.
Though I doubt any royal dukedom or title is without some "history"
Duke of Clarence? probably not, last held by, IIRC, George Plantagenet who was convicted of treason agains this brother King Edward IV during the war of the roses
Duke of Windsor? probably not either. Though I like the sound of that title...its currently extinct and is associated with King Edward VIII abdication, Wallace Simpson.
The 1st Duke of Sussex(Prince Augustus Frederick) was also known for his liberal or progressive views, he fought to abolish the slave trade, and the removal of restrictions on Jews. I suppose he is considered a rebel or one who broke royal tradition by marrying without the Kings consent