If a channel is blown, or the lamp is out, that's a perfect application for status messages. If you look at the ESTA RDM Additional Messages website, you'll see there's already an extra status message there for STS_LOAD_FAILURE
http://www.esta.org/tsp/working_grou...RDMextras.html
If you want to report actual levels, you could advertise a sensor for each output that gives the real level. Sensors are pretty widely supported, but rather low bandwidth. The DMXter updates sensor levels once a second, not sure about other controllers.
With everything you're trying to do, I'd encourage you to attend one of the RDM plugfests. You'll find there are a lot of knowledgeable people around, and lots of different equipment to test with.