In a 'naruto is in a au harem fanfic', aside from the obvious choices like Sakura and Hinata, characters like Temari could be in Naruto's harem. She's from another village and has a strong personality. Her presence would bring in an element of cross - village relations. Karui is also a possibility. She's feisty and has her own set of skills. And then there's Kurenai, the jonin. She could be an interesting addition to the harem, with her experience and calm demeanor.
If the grandfather is very warm and accepting, Shikaneji would feel relieved and happy. They might open up more about their relationship and their dreams. Nejire could start chatting excitedly about their future together, and Shinsou would relax and join in the conversation more. However, if the grandfather is not so friendly, they would be disappointed and perhaps a bit defensive.
Well, one common plot element could be Naruto having to deal with the different personalities of the characters in the harem. For example, if Sakura is in the harem, she might be the feisty one always challenging Naruto, while Hinata could be the shy and sweet one. Another element might be Naruto's growth not just as a ninja but also in his relationships. He has to balance his time and attention among the harem members. Also, there could be rivalries among the harem members themselves, which Naruto has to manage to keep the peace.
Inosuke doesn't become a Hashira in the manga. The story progresses with him having other significant experiences and achievements instead of achieving that specific position.
It's hard to give an exact number. Different story arcs and battles led to the deaths of multiple hashira. Some died heroically, while others met their fate in unexpected ways. The count changes as the manga progresses.
Definitely not. Genya remains outside the ranks of Hashira throughout the manga. This is because of a combination of factors such as his skills, experiences, and the overall direction of the story.