I personally want to see a really badass Naksu. Just like the one we saw in the intro of season 1.
I know a lot of people aren't aboard with this, but I would personally like to see both JSM and GYJ in season 2 together. I want GYJ as Naksu and JSM as Bu Yeon. Bu Yeon has been hinted to be really powerful in season 1 and I would like to see that in season 2. And no, I do not want a love triangle with these two and Jang Uk.
This leads to my second point, I hope they finish off the love triangle? Square? Whatever it is, I would like to see Jang Uk and Naksu in season 2 together. I would prefer of the story shifts to Naksu taking her revenge and Jang Uk and Naksu finding a resolution to this whole AoS fiasco.