We have just returned from a 25 day, 6000 mile trip in our new FB. We found that Airstream did a fantastic job on this floorplan and our AS in particular.
However, WE did not get the convection/microwave instead of just an oven. We bought it off the floor, so no special items were added. That is our mistake.
We bought a small microwave for the counter, but lifting it from the counter to the floor for travel is a pain, and it does take up too much counter space.
So, your idea to switch the door.
I think that we can switch the door and install a heavy duty pull out shelf on which to put the microwave, and pull it out while using it. Maybe even a pull out swivel shelf.
So, it looks like a visit to Home Depot is in order.