They're also stunningly expensive... Do you actually want to make Blood Knights or are you looking for possible BC legs?
Baggronor
I would say the new release of Chaos Knights has made the Blood Knight models redundant. As it was, people used to use Empire Knights for Black Knights in the previous edition. Why they did not make a set of plastic Black Knights is beyond me - with interchangeable arms for wights or vamps.
Sometimes, I really think that the modelling department doesn't communicate properly with the design team to actually enable them the capitalise on their goal of 'selling models' by making rules and models released match.
Of course the Blood Keep Knights are exquisite. But the price you have to pay, especially compared to other models in the range which are comparable looking, but much cheaper mean they are not going to move off the shelves fast enough.