As far as I know, nobody has called the Efreet, so you're welcome to do it, Darthteej. In fact, I was looking through the list of monsters and thinking it was surprising that the Efreet was not yet done.

*Pokes head in*. Um Hi, I think I'd like to do the Efreeti monster class, as differentiated from the Dijjini already made. Don't get me wrong, it was perfectly fine as a way to grant the bare bones genie abilities. However, I'm envisioning something longer and more elaborate, essentially what it does is work as a combination of base and prestige class at 15 level. It's like the prestige Paladin, Bard, and Ranger variants, working off of a pre-existing spellcasting class, and with a very modest base Efreeti race provided. My idea here will be to expand the power over fire that Efreeti have, subitute full spellcasting progression with diverse SLAs, and figure out how to balance Wish in some way, as well as capture some flavor.
My only issue is that you're plotting something "Longer and more elaborate" - standard for working on monster classes is to have the max level in the class tied to the CR. So the Efreet would be an 8 level class.

Can I recommend building off the first 8 levels, with scaling-by-HD allowing for the later content? For example, if you don't like wishes as an 8th level ability, have the "Greater Efreet Magic" section that covers 8th level SLAs explain something like "Finally, at 16 HD, the Efreet gains a specialized ability to grant wishes." Failing that, perhaps build the Efreet to 8th level, and then we can talk about extending it to an 'Efreet Lord' once that's done? You may find you're well and sick of the Efreet by the time you get that far.

Flavorwise, it's interesting to note that (unless I'm somehow distorting legends from multiple sources, here) the legends of Efreet are based around king Solomon sealing the djinn and efreet into servitude. When someone rubs a lamp/ring/sword/gemstone and a djinn/efreet pops out to grant wishes, that's because someone bound them there. As a player, the wishes you get from Efreet are typically because they were bound somewhere or someone is casting (abusing) planar ally. If the efreet is a player, it really changes that whole ball game.