Of the characters they've shown so far, I think I'd try Greninja first. I
adore the character, so much so I raised two of them in X/Y (including a specimen with perfect IVs bred by DaBoss -- thanks again for that, pal!). I was so ecstatic after Greninja's reveal that, in a moment unusual for me, I couldn't describe my hype here so I didn't post much. Instead I paced around the room like I did after the Season 4 finale of Breaking Bad.

The thing with Greninja is he's one of those "dream characters" I'd wish for if I allowed myself to wish for anyone, regardless of how likely they seemed, but when trying to temper my expectations, I would've never guessed him since The Pokémon Company never pushed him more than the other starters. So for him to be singled out for Smashhood... It just never occurred to me as a likely possibility. But I'm stoked it's happening.