Al,
I'm having a hard time picturing a passthrough that wouldn't have a countertop or something else in the way you'd have to lean over when in the kitchen. But I'd love to see an example, too.
Perhaps a vestibule of sorts as passageway, with storage.
Think about the reasons you have to go into the kitchen, now. Supplies, sink/water, prep work. How much of that could be done outside, especially for things that come together quickly?
One thing I'd like is an eating area close to the cookers, with some sun shade.