I think this is basically done, but maybe some parts are bad or uninteresting?
Your base damage is d4.
Your maximum HP is 4+Constitution.
You may be a dwarf, elf, halfling, or human, but it gives you no particular advantage. Choose the source of your elemental powers:
Choose an additional element to master: this element is sacred to your religion and can never cause you harm. You must also choose two elements that are opposed to your religion: you can never master them, and they will deal +1d4 damage to you if they harm you.
A Gift from the Spirits
You can interact (and parley) with elemental spirits as if they were people.
You pay no mind to gods and spirits, but only words of power and the will to use them. You may roll with INT instead of WIS for master of the elements and to speak with the world itself, and a 10+ for eye of the storm also purifies you.
You start with these moves:
Eye of the Storm
When you exert your will to calm the elements around you, roll+CON. On a hit, the world calms around you (the earth below your feet stops breaking apart, fires you touch go out, storms break around you, etc), but on a 7-9, this calmness affects only what you touch, and only as long as you are touching it. You can exert your will over all the natural elements, not just those you have mastered.
Master of the Elements
When you command the elements, roll+WIS. You may only issue commands you have mastered upon elements you have mastered. On a 10+, you may command what is generally considered a large amount of this element. On a 7-9, the same but choose one:
— The elements you command also run wild, out of your control.
— You can only affect what is generally considered a small amount of this element.
— You take an additional -1 ongoing to command the elements until you purify yourself.
If you maintain an unnatural effect, take -1 ongoing to command the elements until you release those still in your power.
If you use your command of the elements to harm someone directly, roll your damage die. Once the elements are released, however, they cause damage as appropriate to their nature.
The Roots of Creation
You start with mastery over one command, one element, and one additional mastery from either list. Each time you level up, choose either another command or another element to master.
Commands: Banish, Create, Destroy, Enhance, Move, Shape, Summon, Transmute.
Elements: Air, Crystals, Darkness, Fire, Ice, Light, Magic, Metal, Plants, Stone, Storms, and Water.
To Speak With the World Itself
When you examine an element you have mastery over, roll+WIS. On a 10+, you learn something interesting and useful. On a 7-9, you learn something interesting, but it’s on you to make it useful. On a miss, you have disturbed the elements with your meddling.
The GM may also tell you something this element wants. If you give it what it wants, it will answer one question you ask of it, to the best of its abilities.
Touching the Firmament
If you have a few hours or so to meditate amongst the raw elements, or to perform rituals before them, they will purify you. This counts as making camp and sleeping, but you do not need to consume a ration. If you spend days amongst the elements, it counts as recovering under the care of a healer.
When you gain a level from 2-5, choose from these moves:
Born of Fire
You are no longer harmed by the touch of fire, nor are you vulnerable to heat.
You ignore the first -1 penalty from commanding the elements and maintaining the effect.
Friend of the Sea
You can live, breathe, and move underwater with ease.
Gift of Power
When you purify yourself amongst the elements, you may choose a command or element you have not mastered. You may use this command or element once only, and then it is lost to you, until you purify yourself again. You may choose a different command or element each time you purify yourself.
Heart of Ice
You can walk easily on ice and are no longer vulnerable to freezing. No matter how cold or slippery it gets, you function fine.
When you use an element you have mastered to deal damage, your damage die is d10 instead of d4.
When you purify yourself amongst the elements, you may also remove a debility or be cured of a disease or poison, so long as the cause of your ailment is not more powerful than the elements themselves.
Shield of Thorns
When you use the elements to defend, on a hit, you may also deal your damage to a nearby foe, in addition to spending hold. You only deal your damage once, even if you have more than one hold.
Choose two elements you have mastered: spirits of those elements will always recognize you as a friend and try to help you, until you prove yourself to be an enemy.
When you gain a level from 6-10, choose from these moves or the level 2-5 moves:
You can transmute your own body into the elements you have mastery over.
When you assume an elemental form, roll+CON. On a 10+, hold 3. On a 7-9, hold 2. On a miss, hold 1 in addition to whatever the GM says.
Your new form can move much like your old form, but has the innate abilities of the elements it is made of: fire burns, stone is hard, water runs and flows, and a body made of light, shadow, or wind is intangible. You still use your normal stats but some moves may be harder to trigger. The GM will also tell you one or more moves associated with your new form. Spend 1 hold to make that move. Once you’re out of hold, you return to your natural form. At any time, you may spend all your hold and revert to your natural form.
Replaces: Elemental Presence
When you command the elements, you ignore the -1 penalty from two effects you maintain.
Friend of the Sky
You can fly, whenever you want, without commanding the air around you.
When you use a command you have mastered to cause damage, either to an element or by commanding an element, you deal +1d6 damage.
The Skein of Creation
When you purify yourself amongst the elements, the GM will reveal to you one grim portent that has not yet come to pass, and tell you which danger it was written for.
The World is My Canvass
When you command the elements, on a 10-11, you may choose one option from the 7-9 list in order to command a huge amount of this element. On a 12+, you can command a huge amount with no consequences.
plus multiclassing at both tiers, but from a restricted class list, and probably the druid’s weather move.