I have read that a lot of Wyandotte breeders get Single Combed chicks. Perhaps you could (or anyone wanting to work on this color) contact a Dunn Wyandotte breeder and ask for their single combed culls. It would be one less thing to breed out.
I'm a fan of jubilee and mottled orps myself. The chocolates are beautiful as well and would make a great project. I'm working on bantam jubilee and mottled currently and hopefully will be able to develop large fowl too, if all goes well. I was going to work on spangled orps, but I changed my mind on that one for now. I love all the projects folks are putting together. This shows true dedication to the orpington breed.
Well I was looking for a photo of a Blue Partridge and I found this photo of a Violet Laced Orpington (I think that is what they are called). Ok drool now!
Yes you would have to worry about skin and leg color in addition to comb. I am pretty sure that white skin/legs are dominant over yellow. As far as the comb goes you would have to breed that out in time. About the single combs from wyandottes, I was on another forum and a couple breeders I talked to had said that they have never gotten single combs from their chocolate wyandottes and I was realizing that when I still had the solid dun birds I had a few people ask for single combed sports so they could make dun cochins and dun ameraucanas and such since the single comb is recessive but in the 3 years we had them we hatched out many many chicks and never got a single comb and the person we sold them to said the same thing, no single combs. So once you get the single comb into them than it is more likely to show up.