Thank you for this, some cool suggestions for future models!
I think especially Valkia is a likely choice for a new model, hope she gets the "Sigvald treatment".
Apart from that I think Khorngors could happen, but it would be difficult to imagine that they could fill in an other role than Reapers/Mongers.
Valkyries or a flying unit in general would be awesome!
In addition I'd like to see a big mortal hammer (Lord on giant Fleshhound/Brassbull) and a shooting unit.