^I've always had a story idea in mind where McGann's Doc revisits the decimated-now-rebuilt Earth of the future where he left Susan. We find out during the story that the 7th Doctor saw the coming Time War, and to protect his granddaughter...his only living relative....he was training Ace to become her guardian/bodyguard. Ace grew up, trained for years under the Doctor's guidance, and then was left with Susan to protect her and her family. By the time McGann returns to check up on them, Ace (who now calls herself by her name of Dorothy) is the age of the actress, and has a daughter of her own (played by a younger actress that can obviously kick-ass like mom) from a deceased husband. So, Dorothy and her daughter (who I named Sylvia McShane) continue to protect the now-elderly Susan, who is approaching her first regeneration.
Do I have a plot? Not so much. Just the character pieces...