Now that is an interesting idea. It might be even more interesting if it wanted to be the Sun - for its flame to usurp the star itself, and thus also the solar system. It's such a nice neighborhood, really, with intelligent life in orbit, worshipers and all that ...
I'm sure Ra / Pelor / whatever sun god and its clerics would have serious problems with that.
Or even more amusing, what if it was supposed to take over for the flame of the current sun, which is starting to die? If the PCs don't find a way to level up this Fire Elemental to ascend to his rightful place in time life as we know if on the planet could be wiped out by its sun going into a red giant phase or a white dwarf phase. Or, heck, since it is fantasy the whole thing could just go nova or collapse into a black whole because fantasy physics is way more entertaining than astrophysics.
Marty Lund
I like the way you think.