If the chat with Nie Wuxing made anything clear it's that we don't need to be worried about him or his ambition. Observe this exchange:
The Ten Swords Conference II
Madam Nie lets out a heavy sigh. “That it may be… but the two of you should heed my words and marry as quickly as possible. Who knows what could happen in the near future… even tomorrow? Life is short. For example, what would you do if my husband offered you Shuixian and Mudan in marriage as a show of his desire to be your comrade?”
“I never-“ begins Nie, but a glance from his wife cuts him off. He nods.
That is whole new levels of whipped.
The fact that Nie Wuxing would be destroyed if the sword was lost in transit is irrelevant, because you can bet the plan originated with wifey, and any attempt to take it will come from her end too.
I can see only two possible goals from her plan to take the sword to Chang'an. And there is a Plan going on here, with a capital P. She wouldn't offer bargaining chips as valuable as the Twin Flowers to gain Jing's support if there wasn't a Plan.
A) Steal the sword away from the island and it's mysterious owner.
For this the talk of patriotism is just a pretext, it's so you don't have to deal with all the other great swordsmen while you look righteous absconding with the blade. Go on to use it for whatever nefarious purposes. But there are problems with this plan; if all you want is the sword then why bring the Emperor into it at all? You have the votes to carry the floor regardless of anyone's arguments, the Sword Saint and Zhang Jue aren't even here, so you have the numbers if it should come to a fight. Just go in there, call in all your favours and take the damn thing. No need to dissemble.
B) Use the sword to gain influence over the Emperor.
This line stuck out to me:
The Ten Swords Conference II
“I believe you have many misunderstandings about us, Xu Jing,” says Madam Nie. “Do you think that we seek to overthrow the Emperor, or to cause him harm in any way? We do not. We are loyal to him and his rule. But the Emperor is surrounded by sycophants and foolish advisors, and if we do not deal with these pests they will do irreversible damage to the Empire.”
The unspoken assumption here is that "I would make a much better advisor." If you crave legitimacy like Nie Wuxing, or have some inscrutable motive like Madame Nie, then handing over the sword to the Emperor makes perfect sense. You ingratiate yourself with the Imperial Court, gain a reputation as righteous and upstanding, and put the most powerful man in the country in your debt. The only person that's going to oppose such a plan at the Sword Conference itself is Zhang Jue (or maybe that lunatic disciple of his, better be ready with some bribes). Remember to them Shun isn't Shun, he's The Emperor, a figurehead sitting atop a vast, corrupt bureaucracy. He's just a man and like any man he can be manipulated.
One possible alternative is that the sword is trapped/cursed in some way, meant to harm the emperor. But that plan is certain suicide for the Nie clan, and I can't believe they'd knowingly pursue it.
So that leaves only the question of what to do about this? Our buddy Shun is clever enough to see through them right? But he could be pressured into fulfilling an obligation to them if the sword is seen to come from just Wuxing. So lets vote
A, having so many formidable individuals in one place should be fun. It's Zhang Jue's idea of a smorgasbord.