The reason I would rather put in Brock over Karen is because Karen gives your opponent back their Pokemon. While this discussion happened when Karen was first announced(That it isn't a big deal for your opponent to get Pokemon back), I believe that it is for Mega Ray, since it seems the 2 worst matchups are Yveltal and PlumeBox(If I'm not wrong that is. I'm sure a few people have noticed my absence for like, the last month, but I haven't really played for that time, either). And giving them back Glaceon, Regice, Fright Night, and Yveltal-EX by itself can be enough for them to come back, not to mention if either of them would be closer to decking out than you(I'm looking at you, PlumeBox), and you need to set back up, you can screw yourself over. Plus, I just like that Brock's Grit has a target limit and can get Energy. While Yes, you do want them in the discard for Mega Turbo, are you ever going to use Brock before you do? And as for Dragonite: I love it!
You can just replace a stadium(If you HAD to for the KO), bench Dragonite, and basically, all you lost was a stadium. I would still keep Jolteon though, for free retreat, plus, it completely destroys Yveltal and Plumebox if you get it set up well. And since all that is-is drawing and energy attachments, you should be golden.
That's just what I came to as a conclusion, though.
Also, all you people that were talking about Solgaleo:
HOW YOU FEEL?