I don't get the need for Vivien to be more kind or more reasonable. Being a protagonist for a set doesn't make her a hero or in the right. She is an **** Steve Irwin and she is one of many planeswalker characters.

I think it also makes sense for green characters to have the most alien morality from everyday real people.

I might be being too hopeful but here's my prediction: Vivien ends up a twist villian. She looks evil, she sounds evil, she's kind if a dick. It makes too much sense really. Wizards did a lot of set up for this gatewatch thing to not bring them back but what do they really have to fight? They took out two of the biggest threats to the multiverse already. Phyrexia is left but we haven't heard from them in a while. I think its pretty obvious what the next planar threat is going to be. The legion of doom. We have a nice array of semi interesting villian walkers still roaming around, some of them probably upset that bolas didn't take over the world, or perhaps some simply wanting to take a page out of bolas' book, they just aren't powerful enough and need a whole team. Unfortunately the bad guys always lose, and in a desperste attempt 8 years or so down the line they free bolas and/or emrakul or something big to take the gatewatch out. Classic superhero shlock

Keeping in mind that Ob Nixilis wiped the floor with half of them single handedly.
I think Ob has the highest chance of being the next centerpiece villain.

A full breakdown of Ikoria
https://www.youtube.com/watch?v=ed4GJgbtJ9I
and importantly how absolutely bungled the story cards are in comparison