Nice mate...I like his padded helmet.The funny thing about this picture is that you and I are both up exactly the same point converting the Shotgun Cultist Champ.....decapitate. PDH
Use a hot needle or something to brand the hydra or XX icon on his shoulder.By the way, will you be keeping/using the Chaos models? I could imagine that the Dark Angel Terminators, with some converting of course, could make nice additional Alpha Legion marines.
By changing just the head and the icon on the necklace (as far as I can tell), you've completely changed the vibe of the model. Kudos! :)