Creating BLRW from scratch?

[nzchick]

I am wanting to create these and I am wondering how they were created in the US to start off with? There are a few people who have created these in NZ but I am wanting to make my own line and not pay crazy price for some eggs that may or may not hatch let alone be what I want.
I am guessing to something along the lines of splash/blue W over a GLW and then later on bring in the Mahogany gene.(I know it wont be that simple! ) Problem is here I have not seen any large breed wyandottes in blue! If they are in NZ they are good at hiding!! So I think I would need to out cross to another breed in the sp/bl to get the colour genes. What breed would be best? (if we have that too!)
I also want to breed them in the silver blue laced but I think that is easier to do from the BLR from what I have heard?
Any advice would be great!!