The One D&D playtest has a revised version of Barkskin that would be cool.
Originally Posted by One D&D UA
BARKSKIN
2nd-Level Transmutation Spell (Primal)
Casting Time: Bonus Action
Range: Touch Component: V, S, M (a handful of bark)
Duration: Concentration, up to 1 hour
You touch one willing creature to protect it with regenerating bark. Until the Spell ends, the target’s skin assumes a bark-like appearance, and at the start of each of the target’s turns, the target gains a number of Temporary Hit Points equal to your Spellcasting Ability Modifier plus your Proficiency Bonus. At Higher Levels. When you cast this Spell using a Spell Slot of 3rd level or higher, you can target one additional willing creature for each slot level above 2nd.

Honestly, the PHB version of Barkskin is terrible. Maybe you get +1 or +2 more AC, at the cost of Concentration meaning you can't cast any other concentration spells. In all the games I've played, a PC has used Barkskin maybe a total of 1 times, and then never again because they realized it's so much worse than all the other options. (I suppose you can get an effective +3 to AC when wildshaped, but then you expect to be in melee -> getting hit -> easy loss of concentration)