I'm having troubles fitting in a starter for me too, honestly. While I do have lots of starters that I like, I don't really consider any of them as Aces, and often, I can find a better Pokemon for their role or in terms of favoritism.
Whimsicott is a really good Pokemon to use, especially if it's in Misty Terrain or the like. Priority Nature Power is nothing to sneeze at, and Prankster Tailwind can make a fairly impossible fight into a cakewalk. (Looking at most of Episode 18's battles)
Does Misty Terrain amplify Cosmic Power even further? That's a pretty cool strategy. A bit too stall-ish for me, but nonetheless, a viable strategy. Intimidate + Snarl is a really cool idea though, I like that. But maybe I'll use it for my Luxray instead of Arcanine. Also, quite nitpicky, but if you managed to have a Grass type to spread Toxic instead of Empoleon, it would be a cool FWG core, though that might mess up its compatibility with your Clefable.
What set do you run for your Silvally? It's a cool Pokemon that no one has as an Ace yet, so I want to try using it. That said, Hyper Offense is fun, but either they get sweeped or you get sweeped. Often I have something with Tailwind/Trick Room/Sticky Web to make sure my team outspeeds the other. E18's battles definitely warned me there.