That's a great idea. With smaller sections of arena we could still incorporate the clock. Maybe the town could look a little like 12 just to mess with them that much more, because Snow is aiming to hurt Katniss? 

That's true. I imagine Haymitch isn't going to be in the best state of mind, so maybe Peeta and the rest figure the less he knows the better. It might be a good idea for either Gale or Prim to know the most, or at least what Johanna and Finnick know. Maybe they figure having all of them in the dark leaves too much to chance. I'm not crazy about 13 myself, tbh. I mean, I like the idea of it, but it just seems so stagnant. While I was reading the books I just thought of it as one big, grey, blob and everyone was bored. So I would be very open to them going somewhere else. Maybe the Wilds, or 11? They feel pretty strongly about the revolution. 

I could see Snow sending someone for Peeta personally. Maybe things don't go the way they should on his end and Plutarch ends up having to leave without him?

I'm thinking out loud as well, so if you don't like any of these ideas, just say so! :3