There’s a lot going on in the greater Descendants ‘verse which I don’t fully know (I haven’t read the book and only cursory watched the animated shorts) so my interpretation of the ‘verse is mostly based on the first movie (I haven’t yet watched the second, but the GIFs look great) and whatever I get curious about and look on the wiki and decide whether or not to keep.
Because the Descendants ‘verse itself picks and chooses what it wants from the greater Disney ‘verse and some of their own beta canon contradicts with itself so it’s hard to keep consistent with the Disney ‘verse when Descendants clearly has decided to ignore it.
I guess what I’m saying is, thanks for the ask, anon, and I’ll answer based on my own internal understanding of the ‘verse (which is based on limited information anyway), and so it is in no way actual factual for the ‘verse and should not discourage you one way or another.
So let’s go:
First off, Moana was a great movie. I loved it. (It’s on Netflix, for anyone who has yet to watch it, btw). And so given, as you said, the Auradon was capable of imprisoning Hades (a full god) and Maui is a demi god (who was born human and whose source of magical shapeshifting abilities is his fish hook) then yes, I agree, that Auradon COULD trap Maui on the Isle. I mean, it’s not even really that difficult since without the hook or a boat he couldn’t leave even a non-enchanted island which is how Moana first meets him in the movie.
Would Auradon think/be motivated to do so? I’m thinking no.
Plot-wise, Maui isn’t really a villain. He’s painted to be so in Moana’s grandmother’s story because, hey, he stole the Heart of Te Fiti and caused the world to slowly decay etc. etc. But then we as an audience find out he was trying to do it for the sake of humans (in a Prometheus-esque, steal fire from the gods sort of situation, and Prometheus was never considered a villain) and in the end, he helps Moana return the Heart which basically wipes his slate clean. Te Fiti even restores his fish hook so, if anything, he’s good there.
So unless Auradon imprisons him before Moana can find him to restore the Heart of Te Fiti–thereby dooming the Polynesian islands/the rest of the world to the encroaching decay and darkness of Te Ka–then he wouldn’t be considered a villain anymore to then be imprisoned.
Additionally–and this is very much so my own headcanon–I’m pretty sure the kingdom of Auradon only corresponds to the equivalent of the continent of Europe. Both the school and the Isle have characters from other countries/kingdoms/empires–such as Jafar and Jay, Lonnie, Freddi Facilier, etc–because the school is meant to foster international relations in the young elites of the world (think actual United Nations for teenagers) and the Isle is one of the most secure prisons in the world.
Maui would be under the jurisdiction of Moana (or her descendants) as the ruler of the society that he briefly terrorized with his actions and seeing as how, again, he did help restore the Heart of Te Fiti, she/her descendants wouldn’t send him to be imprisoned on the Isle.
If anything, the idea that Moana’s descendants have a guardian shapeshifting demigod watching over them at Auradon Prep is a lot more appealing to me than Maui being imprisoned on an Isle and NOT BEING ABLE TO SAIL OR SHAPE SHIFT. That’d be so sad, anon, so sad T_T
And also, considering that some of the GIFs of the second movie have a badass pirate from the Isle, having a voyager on the hero side would be pretty fun.