I also think that there should be a good amount of scenes with Jack and the baby.
From your mouth to the writers pen.
I think a disservice is done to Jack every time someone questions his ability to love his family.
I don't think we were ever really told why Jack distanced himself from Sydney. There is of course many theories and fan fics that discusses the issue, but I don’t think we have a definitive explanation.
I take issue with the idea that Jack abandoned Sydney. He provided her with a good home and a good education. He could have sent her away to boarding school, but he did not. He may not have come home every night, but he did come home. Sydney had that security.
So, to answer your question, yes, he will be a stellar Grandpappy. Unless some unknown force interferes, he will not repeat the mistake he made with Sydney. I believe he will be outwardly, but appropriately, affectionate to the child.
This grandchild will be his redemption. It will be his opportunity to make up to Sydney for the pain he caused her during her childhood. I think in the end that it will also help to mend some of those lonely memories Sydney has of her childhood.
Hopefully Sydney accepts her father’s affection for her child and does not become bitter over it. Unfortunately I think the show has lost some of its ability to show character relationships, but it would be an interesting scenario to see a moment when Sydney shows some jealously over how loving her father is to her child and for her to finally yell at him and share with him the pain she felt as a child. I think the girl needs a good cry over that. She needs Daddy to take her in her arms and tell her he is sorry, and he won’t do it again.