The structure of an Airstream is provided by the ribs in between the outer and inner skins of the shell. The "walls" in the interior are just bulkheads--they don't hold up the roof.
You can get as radical with your rebuild as you have time, money, patience, and ability to support. One thing to consider are the way it is plumbed (in terms of where the tanks are and how the inlets and outlets are set up). You can move the kitchen and bathroom around, but you are going to have to do a lot of tank, floor, and plumbing work to support major relocations.
In terms of electrical, your trailer is already wired for both 110 and 12v
. It may be advisable to leave the 12 v wiring intact, as you may not always want to leave it parked, and changing the wiring irreversibly may affect resale value.
Search the forums for "full monty," and you will see some detailed rebuilds.