D&D 5e Base Class Contest III Chat Thread

[Requilac]

Okay, I finally believe I have came up with something. I was frankly stumped on what to do, so I decided to do some minor research on elementals in mythology. A name that came up a lot was Paracelsus; an alchemist from the 16th century who proposed that their are four types of invisible nature spirits which can travel through their respective elements like we do air. The four elementals were gnomes who could phase through earth (this name is slightly misleading as these are a lot more reminiscent of dwarves than their actual namesake in D&D), salamanders who live and walk through fire (you can find an example of this monster in the MM), Sylphs who could fly through the air (not much different than air elemental in D&D really), and undines who could swim through water (essentially mermaids and similar beings).

This kind of gave me an idea for a class; a sort of shapeshifter who can transform themself into different elementals which decide their features. The main benefit of an elemental form would be what state of matter you could incorporeally travel through, but there would be much more benefits. It is essentially a class that allows you to almost change their form and the corresponding effects of class fatures at will (with resource expenditure), but with the drawback of never having as much raw power as the other classes. Exchanging overall power for unprecedented adaptability. How does this idea sound to you all? I worry that it is running on such strange rules that it may be incredibly unbalanced.