That would definitely work with just one rooster! I thought the same about Naked Necks, but DS has convinced me to add one to my order this year, and after reading more about them, I actually think they are pretty cute in their own way! And are supposed to be pretty docile which is a plus for me.
Just curious how you will keep the flocks separate if they are free-ranging. The only reason I ask is if you have an auto sex breed like Bielefelders running around with other breeds, the other breed roosters will mate with them & defeat the purpose of having Autosex chicks. I do like your plan...