@Deicide:
We could always assume that the marines would give her a ride back to AL anyway. And even if she betrayed the marines, there's some way for her to return, since Nyon was able to bring Hancock and her sisters back to Amazon Lily in the past.
Failing all that, she probably could be rescued by the Kuja Pirates somehow.
We can agree to disagree on this because it's going to go around in circles.
No, I said exactly the contrary, that Hancock's situation is unique because she's endangering her people, and that would require some kind of resolution that I will leave to Oda. This is the kind of information that I simply don't have and can only make suppositions about.
No, you didn't, this is what you said:
Well, Nami, Sanji, Franky, Chopper and Usopp all had to abandon home to go on their adventures. Granted, none of them were endangering their home by abandoning it, but the story is still ongoing.
They aren't remotely similar, unless you are referring to something else, even though I responded directly under this.
Hancock and Vivi are totally different beasts. Vivi's future was with her people; all her actions were towards her people. In the end, she stayed with her people.
About Hancock, however, we don't know how the Kuja determine their rulers. It doesn't seem to be based on bloodline. We don't even know if ruling them is what she really wants for her life. For all we know, she may have been declared Empress because she slew the Gorgon, so she's the empress because of a lie. Her story still need to be developed for us to know her true motivations and dreams.
They are not entirely different beasts, both had an entire society/country depending on them, their personalities, and thought processes might be different, but in the end they have the same obligations to their people. Actually, Vivi doesn't have as large an obligation yet, she is ruler to be, while Hancock is the ruler of her people.
Whether the ruler of the island is based on bloodline or not, she is the ruler and seems to have been for quite some time. With the personality Hancock has, you can really see her not wanting to rule over people? That entire story you hypothesized as a possibility for her reign as empress still doesn't change the fact that she is their empress and can't just abandon her people after they have depended on her so long. Her rule could be a fallacy, but that doesn't change the fact that her people seem to be prospering and safe under her rule, why would they want to dethrone her? She has an entire island depending on her, she can't just abandon them because she feels like going sailing with Luffy, what kind of Strawhat is that?
Check the part I bolded in your text. If Hancock's being set to join, then Oda already knows how he will resolve this plot point. I won't try to point solutions, because I've already done it in this thread and past versions of it, but all solutions pointed are always flawed in the views of others, so I'll leave that to Oda if Hancock ends up joining the team.
That goes both ways, if Oda wanted to write a way for her join later in the story, he could have just made all these hindrances a moot point. He's put a large amount of barriers and plot points he needs to fix before he can have her join, and is even enlarging them by having her continue to defend her title to the Marines while stealing their ship. There is simpler methods for him to write her entrance in the crew, rather than now having to deal with her island, title, and all the people that depend on her.
What makes you think that Hancock joining would delay fishman island? The "Amazon Lily is endangered" arc could play out later on the story, and not even involve the Strawhats returning to the first half of the Grand Line. Hancock's joining may stay a secret for quite some time. And there may be different resolutions that don't need an entire arc to be done. It's not like Luffy has the power to stop the marines and save AL right now.
See, even in my last post, you ignored what I said about the fact that it degrades her character to even attempt to join Luffy, while she knows that her title hands in the balance. She holds the key to lives of hundreds, maybe thousands with her title as a warlord and she's going to risk it for her feelings? That's basically spitting all over the developed traits Oda has had in being a member the Strawhat crew, and then there's dealing with how Luffy can accept someone so selfish on his crew. She's basically the epitome of the people Luffy hates, she wouldn't have a care for people back on the island because she gets what she wants.
It's either deal with this now and have her join the crew without any burden of her people or go with Luffy knowing full well she is going to lead to her island being destroyed at some point. The part I bolded was one of the reasons I explained in my first post for why this probably won't be dealt with now.