I think a pass-through window is key.
For years I've dreamed of a patio just outside the kitchen door, to shorten the movement from the inside to the outside. But as I've moved my grills around for various reasons, I've found that it works *much* better to have the grills near a window instead of a door. I have some kind of table immediately outside the window, and this is a perfect place to stage food to go onto the grill(s) and then back into the house when it's finished. There's much less transfer of air (summer or winter), and I don't need to walk the food to a table-- the table is just a lift of the window away.
And I second the skepticism about having a sink or counter on the inside of the window. In my experience, that would be pointless because there's no need to put food *inside* the kitchen-- I just set it directly outside.
Another thing I've appreciated about this setup is that when I'm cooking overnight, I just stage the smoker right next to the table. Then I can *see* how my smoke is working, and just generally enjoy the ambiance. And even during the day, there's nothing better than glancing outside to see the beauty of a smoking session in progress.