Guys, thanks for great feedback! This is my first time with scrap building, so any thoughts are highly appreciated!
@death_scythe: Thanks for kind words! Don't get me wrong,
HD model itself is great, but I don't like the idea of a dragon in
CSM army. When you look on older machines made by Dark Mechanicum you will not notice similar animal-like shapes... Chaos is meant to be weird, odd and frightening. But that's just my taste

So I don't want to have any claws etc. Highly stylised head might be good though - I will try to make something.
@clively: Haha, thanks. Well I tried to mimic the shape of
HD after all, hence wings done that way.
@kuzao: You're right. I need to make the first one less flat.
@Rotgut: Thanks, that look of possessed fighter is exactly something I tried to achieve here.
@btldoomhammer: Wow, man. Thanks for comprehensive feedback! Yes, blight drone idea is perfect. I considered that, but didn't had anything to make rotors. I saw once a model made from old (small) CPU fans, unfortunately I didn't had any. Doing them from scratch is beyond my abilities

I gave Nurgle one to my friend, so let's see what he will do with that

For now I will focus on 1k sons. I was thinking about using flesh there and in the end decided that
HD as a daemon wasn't affected by Rubric of Ahriman. So your hint to make some Tzeentch-like mutations is probably something I will use. I'm thinking also about what kuzao said, so I need to make this fighter less flat.
@xraytango: Glue is there to mimic flesh melted together with the metal. I was trying to get an effect similar to mutilators etc.