@LeaD:
She had no other way if she was planning to follow Luffy, other than the Marines. Ships that can traverse the calm belt are few and far between it seems, other than the Marines. The Thousand Sunny has the means to travel in the calm belt.
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.
You basically shot down your own point here, and are you trying to say that because they left their homes, they could have endangered it for some future threat to their island?
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.
What? None of them abandoned their homes, they left of their own accord, and didn't have positions that required them to remain on their island. All five of them really don't correlate with the circumstances that hinder Hancock, except possibly Franky, who really just lead a bunch of gangsters that became good people. That's not taking into the fact that his "gang" is perfectly safe whether he is there or not, Water 7 is in no danger. Hancock is the leader of an entire island, her position in the government is what allows them to stay safe, and she has possibly thousands to look after.
The only person that really had a background that could match up in some facet with Hancock is Vivi, who didn't abandon her people to leave with the crew. That's not even considering the fact that she is only being groomed to lead her people, while her father looks to be pretty young himself.
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.
No, it isn't subjective, if she goes with Luffy and is found out, she loses her title, and her island goes away. Why would the Marines allow a known pirating society, a strong one at that, survive if they are getting nothing in return? Especially since the leader of the society just decided to join with one of their most dangerous up and coming threats? How does it not degrade Hancock's character if she goes with Luffy knowing full well she is risking her entire island? Why would Luffy ever allow that in the first place? That sounds like the type of thing that would enrage Luffy, and even the rest of the crew, it's completely selfish and risks the lives of many others to indulge in her feelings.
Yes, it's up to Oda to write whatever he likes, but being the diligent, thorough, and pre-planning writer he has shown himself to be, he's not going to write something in bad taste. If you want to argue on that basis, why don't we just say that Oda can write Ace coming back to life and joining the crew because anything can happen!
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's the point, he has been "dangling" Fishman Island for a long time and he knows it better than anyone. The story has been at the precipice of the New World for a long time, there's been tons of foreshadowing, and we've just seen Luffy get a taste of what awaits him, but we're going to go backwards for an Arc instead?
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.