Summary
Went looking for your post.
Moffat’s idea with the vicar plot was him and his family have to make the worst possible decision at every turn. If, for whatever reason they do a second, Tucci and Dolly Wells would come back but they would have a new main plot that the pair are aware of.
I suspected Dolly Wells’ character is the not as dead as they claim wife, as she seems determined to keep a mystery then, more than once, you see her doing the complete understanding of a room that Tucci does.