Very interesting. I wouldn't be against such a thing, because I do love being able to reconcile changed premises in-universe. But if we assume that Hartnell-to-Troughton was a rejuvenation and Troughton-to-Pertwee was just a change of appearance, how do we address the changes in personality? I suppose rejuvination could effect one's prersonality, personalities change with age. But the Second and Third Doctors have very different personalities (and heights!) How would that be explained?