What is your mandate to use
GW parts? Are you stuck playing in a
GW store so need it to be legal for play? Or is it simply preference?
The acolyte of the celestial hurricanum would be a good starting point if you're set on using
GW plastics. Be aware though that you won't get something as dynamic as the examples you showed.
Personally, I've had good experiences with mixing those reaper models and
gw bitz.