Hmmm, I can't really think of any off hand, im not a great fan pf the daemonette models but then again none of the Slaanesh stuff ever appealed to me so I'm not really bothered.
Also I like the possessed models, yes the armour's mutated because the daemon inhabits the body of the the possessed marine and the daemon's mutating influence leads the armour itself to twist and change, and in that process some of the armour does indeed fuse with the daemon/marine, remember that the daemon doesn't distinguish where the marine ends and the armour begins, especially seeing as the two are attached to each other.