Even though this team is instantly the best on the Subway because ponies, I can still give my two cents in items, I guess? the rest of the team looks good, and I put this as an answer just so RD can be epic up there.
For Pinkie, I'd give her a Leftovers with Storm Drain to shake off substitute damage. I see the lack of appeal in a Life Orb for obvious reasons, so maybe an Expert Belt, thanks to the decent coverage?
for AppleJack (best pony, teeheehee!), I'd give him a Big Root, just so that Horn Leech recovers more HP. Something like a Muscle Band could work as well. Or maybe you had no intentions of items for a reason and I missed the point. In that case, downvote away. :P
Still, I love this concept. Great job!
(sorry that it's so big)