We like to have a window open at night, weather permitting, so we generally keep the fire exit window propped open with a stick, since it is the only window close to our bed. If I were to replace it with a door, I would want to have a window in the door that opens. I'm not sure if this would be possible with a typical Airstream door. I know the front door has a stupid opaque window that you can't see through, and I've enquired of AS whether it would be possible to replace it with one that I can see through. AS says no, which leads me to strongly suspect I couldn't get one that opens, either. Of course you could have the whole door custom made and probably put any kind of window you wanted in it, at a fairly high cost, no doubt.
As far as fires are concerned, my feeling is that there probably won't be a fire that I have to escape from. In the unlikely event there is, I'm sure I'll figure out some way to get through the window, albeit with some contusions, perhaps. For a person more concerned about that than I am, but still unwilling to spend big bucks on a custom door, I would suggest propping a 4' lightweight stepladder right below the window at night. There are times I have wished I had a small stepladder, so it might be useful for more than just escaping from a fire unscathed.