How do I setup 4 Player Battle Camera?

So I'm working on making a 4 Player battle arena in the same vein as Super Smash Bros and Duck Game.

Duck Game

Basically where the camera zooms in and out based on the distance between all the players. I've seen a couple of things on how to do it with only two players. The ones I saw though weren't really translatable to a 4 player game and all the zooming had the level zooming out to the far left corner and not keeping things centered.

Anyone have any ideas on how something like this might work?

Something like this? https://dl.dropboxusercontent.com/u/135 ... .capx?dl=1

I really like your solution. i'm going to work it into my project and mess with it a bit see if I can get it working the way I want. Thank you very much. I'll post again once I get it going.