I can tell you from conversations I've had with a vendor who has created alternate uvs that wasn't the case. It's more a case of painstakingly matching up the edges of the uvs in a program like uv layout. It's quite involved and requires hiding the parts that aren't on the uv map that you're working on. So if you work on the head you hide all the other bits. My skills with UV Layout aren't good enough to do this yet, but one day I will unfortunately it is a project I wouldn't be able to share... : (