Wild Druid is not a weak option for Druid, something I wish to lay down transparently. It's not a place of balance that brings me to this idea, as Untamed Form works within it's currently intended purpose: a robust, action intensive tool to become reasonably competent in martial combat in a required situation, trading in your spellcasting power temporarily while maintaining it for other situations.
But I believe that there is a strong fantasy in the archetypical niche of Druid, to still retain some magical abilities while shapeshifted. My inspiration came from the Elemental Instinct Barbarian, and their Rage ability to grant the 'Rage' trait to elemental impulses they pick from Kineticist Dedication (provided they share the same element). So I came up with a trait: "Wild Trait: You may use actions with the Wild Trait while under the effects of a Polymorph effect."
I have no set framework for how this might work at present, and really only two ideas. One would be to allow for feats, such as Grown of Oak from the Leaf Order feat line, to also grant the given spells like Oaken Resilience the 'Wild' Trait, or similar feats to allow similar spells to function in Untamed Form, with the intent that this trait should primarily be for buffs that can function within Polymorph's limits, certain Crowd Control area effects, and possibly Heal.
Another idea would be to directly work akin to the Elemental Barbarian, and give the 'Wild' trait to Kineticist Impulses.
And a third hypothetical suggestion that is pure conjecture until we finally get Divine Mysteries, is a class archetype using what we end up seeing for both Battle Harbinger Cleric, and Bloodrager Barbarian.
As I stated at the top, I don't think Untamed Form is weak, which is why i'd be really hesitant to simply make these free and not class feat taxed. This concept comes from a place that may simply be inspired by the fact that I am the primary user of the Divine and Primal spell lists at my table, and found it a lot easier to maintain my 'gish' style as a Warpriest still having access to heals for allies in an emergency, without having to surrender a full turn to become martial-relative again. Often times it feels like, unless an enemy is directly on top of me alone, Wildshape just came at such a great risk of not being able to support my team properly should a wild crit take an ally down, who I have now effectively felt like I have removed from the game because I chose to shapeshift and now cannot do what is required to let him play the game again.