Base Class: Wizard
While you may have not grown up in a Druidic order, you have always been fascinated by nature and the magic used by Druids. Despite lacking the natural ability to become a Druid you've dedicated yourself to mastering elemental magic and unlocking the secrets of harmony with nature in the pursuit of greater power and insight. Through intense study and long stretches of time spent in environments saturated with natural elemental energy, you've developed a unique way to use Druidic magic and have become an Elementalist.
Level 3: Druidic Scholar
When you gain a feature from this subclass other than this one, you also learn two spells from the Druid spell list that are of a level you can cast but are no higher than 5th level. You always have these spells prepared and they count as Wizard spells for you.
Level 3: Elemental Protection
You've learned to protect yourself with elemental energy while using Druidic magic. When you are concentrating on a spell granted by your Druidic Scholar feature you gain a +2 bonus to your Armor Class, and you can add your Intelligence modifier to your Constitution saving throws.
Level 6: Nature's Ferocity
Your connection to nature grows stronger as your studies continue and your body adapts to elemental energy. Your Hit Point maximum increases by 6, and it increases by 1 whenever you gain another Wizard level.
Additionally, while you have the benefits of your Elemental Protection feature you can cast a Wizard Cantrip as a Bonus Action and when enemies deal damage to you with a melee attack they take Acid, Cold, Fire, or Lightning damage (your choice) equal to your Intelligence modifier.
Level 10: Elemental Guardian
You learn the Summon Elemental spell, always have it prepared, and you can cast it without a Material component. If you concentrate on this spell you gain the benefits of your Elemental Protection feature.
You can cast the spell as a Bonus Action instead of an Action. When you do so, it does not require Concentration and does not cost a spell slot, but you cannot cast it in this way again until you finish a Long Rest.
Level 14: Master Elementalist
Thanks to your study of Druidic magic, you achieved true harmony with nature and have gained the ability to masterfully control elemental energy to protect yourself and your allies. While you are concentrating on a spell granted by your Druidic Scholar feature, you and all allies within 10 feet of you gain the effects of Half Cover and Resistance to Acid, Cold, Fire, or Lightning damage (your choice).
You chose the damage Resistance granted by this feature when this effect is activated and can use a Bonus Action on subsequent turns to change it to a different Resistance from the options available.
I wanted a Wizard that focused on "nature magic" that facilitated a melee or ranged playstyle while also doing something interesting with the idea of an "expanded spell list" for Wizards. This is also the kind of spellcaster fantasy I feel has been lacking from D&D, basically a person who studies nature and the elements but was not raised alongside it like a Druid.
The Druidic Scholar feature effectively gives you 8 additional spells at Wizard Level 14, which can all be Druid-exclusive spells that you normally would not have access to. This also makes the total number of prepared spells for Wizard roughly in line with most Druid subclasses. The other features are self-explanatory, but I will point out that the 2024 version of True Strike works really well with the Nature's Ferocity feature.
I hope you give it a try and enjoy it. Let me know what I can add, change, adjust, or improve.