“Doctor! The Daleks have returned for the (insert big number here) time!” *Doctor starts crying* “There’s not enough time to get your paci!”
I think that the baby doctor could work for an episode. Like he turns into a baby, and the companion has to turn him back while avoiding the bad guy AND trying to bring herself to physically harm an infant enough to approach death and regenerate. It would be a real nail-biter of an episode.