Its kind of funny that of all people to rain on your parade it would be me, a motorhome guy..........None of you trailer people told him about this.
Renovating a trailer is more science than design. It's the reason most people get to the stage you are at, and then give up, for the simple reason......they forgot to section off their trailer and weigh everything that comes out of the sections. How else are you going to know what weight you can put back, and where. Now you're going to have to science the crap out of this.
Find the Airstream stock weight, empty and gross weight full of your trailer. Section off the trailer into four sections (two equal ahead of the axles and two equal behind); and weight everything that goes into these sections If you can, add a middle line to weigh side to side. You will also need a weigh scale under the tonque to set tongue weight.
Whatever cabinets you make will have to be as light as possible. Mine I made for my motorhome have no bottoms, backs or even tops, other than countertops.
Remember to add everything that you intend to go camping with into whatever section you will need to store it in. If you create a lot of storage far behind the axle, while empty the tonque weight will be fine, but fill the storage full and all of a sudden your tonque weight could be negative (very, very bad thing).