I had given some thought about making an elementalist also, I think it is a valid and needed class. In my line of thinking I wanted the elementalist to have a completely different feel from the wizard and sorcerer. To accomplish this my ideas are:
1.) model the class after the warlock class from 3.5 but instead of eldritch blast it would be elemental energy. I like this approach because the class seems to be channeling the elements instead of using formal spells.
2.) The class would start with one element (energy type) at first, but would be able to acquire others and other abilities similar to way rogues/magus/gunslingers gain their abilities. These abilities would also replace the feats for the eldritch blast that the warlock would use to modify the blast.
3.) Allow the class to gain an elemental companion in a manner similar to the summoner's eidelon. I would also allow for a mephit familiar.
4.) As far as hit dice, I would go with d8. I would give average skill points. Attacks and saves would be similar to the wizard and sorcerer, although I might allow light armor.
Just some thought to share with you.
