Using the Favored Soul as a jumping point, and running with a suggestion I'd read over the weekend, here's my take on the Nature's Warden - a druid based sorcerer.

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Nature’s Warden
You have been infused with the power of Nature. Perhaps there are traces of the feywild in your ancestry. A mighty druid might have sired your lineage in a primordial age, or other champion of the wild places long ago. However it came to be, the power of the natural world ebbs and flows in your veins.

Naturalist
At 1st level, you obtain all your spells from the Druid spell list rather than the Sorcerer spell list. Additionally, you can choose to cast spells using either your Wisdom or Charisma as your casting stat. Once chosen, it cannot be changed. Note: You're still a sorcerer, you must still choose your spells known, unlike a druid who prepares their spells.

Bonus Proficiencies
At 1st level, you gain proficiency in light armor, medium armor, shields, and simple weapons. However, you are restricted from using metal armor, as per Druid.

Land’s Stride
Starting at 6th level, moving through nonmagical difficult terrain costs you no extra movement. You can also pass through nonmagical plants without being slowed by them and without taking damage from them if they have thorns, spines, or a similar hazard. In addition, you have advantage on saving throws against plants that are magically created or manipulated to impede movement, such those created by the entangle spell.

Thousand Forms
By 14th level, you have learned to use magic to alter your physical form in more subtle ways. You can cast the Alter Self spell at will.

Undying Sentinel
Starting at 18th level, when you are reduced to 0 hit points and are not killed outright, you can choose to drop to 1 hit point instead. Once you use this ability, you can’t use it again until you finish a long rest.
Additionally, you suffer none of the drawbacks of old age, and you can’t be aged magically, aging only 1 year for every 10 that pass.