I think he probably sees the character as more related to his own rather than necessarily the same character in a way. Reading the books, you can see why Sidney would be the way he is as the writer based him on his dad-kind and self-deprecating but not terribly exciting.
He has two women interested in him, but even that is a bit like a comfortable tale someone would tell about their parents, "My mom was so beautiful a prince himself threw himself at her feet, but she only had eyes for my dad" kind of boasting. When the spoilers mentioned come along, he is still just a nice middle-aged reliable guy whose worse sin is not liking people offering him sherry all the time.
In the show, you got a young viral actor who has more appeal hopping off his bike than Mr. Grey with a crop. He can also portray a range of emotions and you have to keep the audience interested. Not everyone is going to care about the romance angle, but plenty are. So that is why I think we are getting Hildy heading off. In the book she is in Grantchester after being in Germany specifically because of the spoiler mentioned, why on earth would she have returned otherwise? It reminds me of Miss Fisher's Murder Mysteries if you watch it on Netflix. In the book she has a ongoing relationship, but in the show the man was in two episodes and then gone forever. I think Hildy and Amanda are in the show because they are in the books from the start and the adapters are honoring them for the readers, but now Hildy has no reason to be there and Amanda can pop up from time to time for angst purposes but be dropped when they don't need her. Bring on a new girl or keep him without a girl for a bit. I would rather spend a bit more time on just his relationships with his favorite copper and curate.
I thought for sure the abused wife was coming up behind her husband to shoot him.