Oddly enough, I have been planning to have the PCs in the next campaign I run taking on a cult dedicated to freeing the mad goddess of elemental fire that the dwarven god had sealed away thousands of years before. I had originally planned on putting their base in a bog-standard volcano, but the idea of a fire font seems much more appropriate. More to the point, the archons would make these cultists a credible threat to the dwarves, especially if they have found the means of constructing a forge to mass-produce them by slaying other elemental creatures. Of course, it will be up to the PCs to figure out how to put a stop to that...
I certainly won't be replacing all the archons with elemental ones, since I already have gone out of my way to account for their existance in my homebrew's cosmology, but I don't think the term needs to be exclusive.
Robert "Burninating the Countryside" Ranting
P.S. Delta, scroll down to the bottom of the webpage and click on Printer Friendly Version. That's what I do.