Biggest question I would have for you is if you intend to sleep in the trailer, and if so, really consider what you'll need for space in order to do so. Summer comps can be brutually hot and glad that my teammate and I are able to sleep in ours (7 x 16 w/o porch) in the A/C. We use two zero gravity chairs, but admittedly, we sleep in the space where the smokers themselves sit (two Superior Gravity feeds). If we had a porch, there'd be no way we'd be able to sleep in there with given, as a fair amount of space is taken up by cabinet space and the fridge we've put in it (26" x 26" Danby Fridge). If you can build in foldable bunks against the back or side wall, you'd be set as you'd still have room w/o sacrificing too much.
Other small considerations - a couple windows to get a cross draft when its not too hot, upper cabinets, any e-track / tie down points where you'll be hauling items such as chairs, tents, tables, etc. Put a GFI plugin on the outside of your trailer, both in the back at the smokers but also in a side where you might have a tent / outdoor entertaining.