The result is Durak Rask, Siegemaster of the Death Guard Legion:
I think the new Thunder Hammer is much more '30K' than the original. The Volkite Serpenta pistol was produced by cutting down a Caliver. I'm sure that FW will produce a proper one in due course, but I think this looks okay.
Of course, this now means a proper FW version of the good siegemaster will appear shortly ;-)