Welcome to Librarium Online!
Just started a new Raven Guard army involving many gribbly conversions.
Raven Guard have lovely looking lightning claws (see WD with the rules).
I would recomend cutting staples ang glueing then to power fists. these look amazing!
I would have done something similar, but sythes tend to look a bit to Chaosy. Sounds alot easier though... my version involved much bonding between power fists and fingers...
I have also constructed a command squad using those perfect minitures from the Blood Angels Honour Guard set, and stuck an extra sword and jump pack to the Emperors champion to form one hell of a commander!