From my understanding, Kroot can take on the attributes of what they eat.
Therefore if you feed one enough winged food, it should gain wings...
Also, if a Kroot's arms were wings, how would it hold a rifle?
This is my answer.
Feathers were sculpted from epoxy putty.
Feet were cut off and a rifle with the hands conveniently spaced, was attached with minimal alterations to the legs.
Final set of photos of the flying kroot conversion.
While the outer feathers are painted with reference to your average bird, I painted the inside of the wings a bright yellow so they could use it to dazzle the enemy or maybe even a mate.
The pilot of the modified Wave Serpent, true to my army's form, is just a head supported by a mass of wires.
You can just about see his grin through the cockpit window.