"One day I shall come back. Yes, I shall come back. Until then, there must be no regrets, no tears, no anxieties." -- The Doctor
One of the great storytelling devices in the Doctor Who franchise is the lead character's ability to regenerate when he becomes too old or mortally wounded, obtaining a new body and personality (and played by a new actor). It's a brilliant premise, allowing all the decades of episodes in the various incarnations of the series to fit into the continuity of the story. So when a new actor comes aboard, it's not a total reboot of the show, it's a continuation. It allows for changes and reimagined tinkering with the character, but it secures everything that's come before without negating it. And, it enables the writers of the series to once in a while reference what's come before, and build on past adventures. It also allows every fanboy's dream of having appearances by multiple Doctors through time -- the ultimate Time Lord scenario.
Now here's my wacky, off-the-wall idea for a similar plot device for another beloved British character who has been portrayed by a number of different men over the years. I'm talking about James Bond.
Why not make Agent 007 a designation that is passed down each generation? James Bond would be a code name that is earned by whoever can prove to be worthy to fill the tuxedo. My idea would then lead to a film in which we brought back all the previous James Bonds who are in retirement. Maybe an assassin is trying to kill them all off one by one and the newest, young Bond is the only one who can save them.
Such a story would provide continuity for a franchise that's been around for half a century. Every time a new Bond is cast, it wouldn't have to completely ignore everything that's happened in the previous films, but at the same time allow the filmmakers to make a fresh start with a new actor.
Hey, it works for the Doctor.