Well here's an Idea. How about using the Red Terror?
I got my hands on one a while ago and I started to convert him for a Doom of Malan'tai. It's an awesome figure you can't use any other way in a standard game so converting it should do it justice

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RT has a very long tail that can be modeled very easily, you just need to redo the torso a little bit, add the wings and some other bits and youre ready to go!