X-Plane 9 has a number of recent features to let you customize the exterior lighting of your aircraft; see the wiki for notes and a sample plane.
X-Plane 940 introduced the concept of parameterized lights to support these features. Here's the basic idea:
Named lights (available for quite a while now) let you add a light billboard to your model that we define. The idea is that since the lights are specified against a real world model (this light billboard should look roughly like a landing light) it lets us upgrade art assets and back the light with the fastest path on the graphics card.
The problem with landing lights is that they are one-size-fits all, and this is particularly problematic for airplanes, where the lights can look quite different in size and angle based on the size of the airplane. Parameterized lights fix this by letting you specify a limited number of parameters in your OBJ. By limiting the parameters that you can set, it means that we can still optimize the light when possible.
I took a few minutes today to round out the list of parameterized lights, and I think there will be 9.46 patch in which we can release them*. When we put 9.46 in beta I'll update the example plane; the new set of lights will give you parameterized control over the navigation and taxi lights, as well as the generics, beacons, strobes and landing lights.
* We have a few small bug fixes we'll roll out in 9.46.