It just seems so very unnecessary to me, and I'm sorry, but... silly. I could never take Missy seriously as the Master. Some other female Time Lord from the Doc's past, sure, no worries, but the Master...
really?
And the same applies. Whittaker looks like she'd make an ideal new incarnation of Romana in a spin-off show... but so far I just can't stop myself giggling at the idea of her being the Doctor. It just seems so forced and... silly.
