while completing the exporter for XSI i've noticed that emitting object are defined on the base of a property related to Object state and not on material one. This behaviour, for example, doesn't let the user to make a different faces of a single object to act as an emitter and as a receiver because i've understood that emitting property couldn't be assigned like a material and triangle-set. Moreover doesn't let the exporters to handle the incandescence parameter that usually are present in the Material Management panels.
Isn't wiser, in your opinion, to redefine the capability to emit light as a different "shader" like diffuse, phong, specular, RGB Emitter, BlackBody Emitter and so on? This is much more versatile but i dunno how hard could be to embedd such a modification in your code.
Give it a think
Best wishes, Riccardo.