I would personally go with McMourning. Von Schill is one of the games hardest Resser counters, as he has access to models that can remove corpse counters (Specialist) and can make himself and even his crew immune to horror duels, not to mention his crews higher than average Wp. For these reasons, I don't think Seamus or Nicodem are a good idea. Instead, I would play the armor ignoring, poison inducing, no need for corpse counters Doctor. I would also take plenty of scheme runners in the form of canine remains as well as support models like sebastian and nurses. I also wouldn't focus on killing the crew, but scoring as many of the marker placement schemes as possible. Tie up the center with McMourning, Sebastian, Nurses, and some meat shields like Flesh Constructs while all the doggies run the flanks dropping markers. This is just me though =).