Kannik
Legend
I've always liked elementalists (been playing them since my DM made one in 2e, prior even to the Tome of Magic being released) and I very much concur that the Essentials version felt well put together (I say only felt because while I started one that campaign ended before I got a chance to play her through and see if it was indeed a well constructed class).The Elementalist is, in my not so humble opinion, one of the best things to come out of Essentials. It is the first truly, actually SIMPLE spellcaster in D&D history. Warlocks were always fiddly, and regular casters have a bunch of stuff to memorize. The Elementalist, at least to a more meaningful degree than any previous attempt, actually made good on the idea of a class that was unequivocally magical, undeniably doing magic, but in really straightforward, easily digested ways. The only other rulesets I've seen achieve this are 13A and (to a lesser extent) PF Spheres of Power, and even then I don't think either did it quite as well. I would not promote the Elementalist to being its own class though. It would simply be one of the main build options for Sorcerer: a more fixed, linear model for those who want to make just a few choices and then get to the MAGIC baybee!
If all the classes/subclasses/builds listed as part of them whether which bits of the AEDU structure the character uses, it might be easy enough to fold into the main Sorcerer class.