Hi Cynthia - sounds like you may be having a breeding adventure next season - will be exciting to hear about it.  From what I have been told/read, people could use gold laced or silver laced Cochins instead of the Wyandote, but it would take a few years to breed out the feathered legs etc back to Orp type and shape.  Likewise with the Barnevelder - this could be used, but it would take a while to select against those yellow legs.  To my mind, though, if anyone already has Cochin/Barnevelder, it is worth a go, because it is a long-term project anyway, using the Wyandotte, getting the all-over body lace pattern and breeding out the Wyandotte shape to get back to the Orp standard.  I am no geneticist but possibly an advantage with some people using Cochin/Barne is that if they swop eggs 2 or 3 years down the line, to head off inbreeding problems, the birds will be reinvorated with the different bloodlines.