Actually, I think he could do very well at 175.
Pascal would be a big test but I think he would beat the likes of Cloud, Braehmer and Shumenov. Those three guys are just beltholders. The best 3 fighters at 175lbs are Pascal, Hopkins and Gabriel Campillo.
Kessler should move up. There's not much left for him to accomplish at 168. He might see it a different way but I think 175 would be great for him.
Height and reach and 2 things his style relies quite heavily on, he would be fighting guys almost as tall or as tall as he is at 175 and above.
This
If Kessler get's outjabbed he has no hope.