@Weirdo here's why I like Arianne: very smart, capable wife our age who comes with Westeros support (Dorne support isn't guaranteed since Aegon is around, this nips that in the bud) who is guaranteed to be loyal and helpful (since word of god aka word of magoose says at least one of the girls is an assassin planning to kill us but that Arianne isn't). She comes with all the sand snakes to be Dany's ladies in waiting which means a whole group of talented capable subordinates. It also eases dornes demands for vengeance on Lannisters/etc since we're giving them something else and we did promise Jaime to show leniency to Cersei. Also, Arianne is also just a fun person.
Maybe we just read it differently, but I've read it as Dorne is our strongest supporter in Westeros except for the Iron Isles, they rolled highest, higher than the North. The thing with Aegon I thought was resolved? He pledged his support for us 2 updates ago, so that is already nipped in the bud. So, I think Dorne's loyalty is pretty much guaranteed
On the loyalty thing, the Valyrian is unlikely to be an assassin, if she was then they wouldn't be demanding conversion in order to speak, they'd want us to really want to pick her. So, I think it's not too much of a problem for us here, at least when comparing these 2 as marriage possibilities.
On the Sand Snakes, I don't really know their capabilities, so I don't know how useful they are, and so can't really evaluate them. They sound like spies + body guards, which are useful, but I just don't know if it's worth not getting the political support of a new person. But, special units, if in large enough quantities and we'll trained enough is a fair enough reason to take a marriage candidate.
On the Lannister issue, couldn't we let them take out their anger on Tywin and others in their province? In order to give leniency to Cersei, we offer up harsher punishments to people like Tywin Lannister and some other people important in Westeros politics, but that we don't care about
