You can always run some kind of Moody Glalie set :PI did look at all OHKO possibilities and I think those are the scariest for what I'm trying to build with. I should have added the Glalie set on the list too, that's my fault. But no way in hell am I making Silvally an Ice-type I'm too scared for that x).
Have you considered a fast Substitute user and fish for a miss?
By the way... I noticed the game lets you add trainers as potential partners even if you had done so already (say, you add Cynthia, then you fight her again and you can still add her as a partner). Is there any difference if you add the trainer again? If there is, I guess it's adding the Pokemon that trainer used in the last battle to his/her potential roster.