You mean something wrong besides it blatantly contradicting all we know of the Doctor's early years and regenerative cycle up to this point?
Remember, Moffat got away with Warrior only because 1) Nine wouldn't come back and 2) it's John freaking Hurt. Throw a never-hinted-at pre-Hartnell girl incarnation in there - and seriously mean it - and he'll envy late-80's JNT in terms of fan wrath.
And he'd care what 1% of the audience thinks?