Wait 'till all the forgeworld boni have been leaked and take the most resilient of them

. I'm partly with purifier here, though I also think it really depends on the scale of your conversions. Are they green Admech units with some rust or are they highly corrupted "plague-skitarii"? if it's the latter and you really fancy Nurgle I'd say find a way to use them as either
DG or
FW proxys that your opponent can easily understand. Plasma-calivers being plasma guns for example.