"He who marches out of step hears another drum." ~ Ken Kesey
I like Danny's approach. Also, probably just straight waterbase black thru a 305 mesh cut back to 65-70% halftone fill to allow even more of the shirt texture to show thru even more. This would allow for even more of a softer hand than a solid black fill of waterbase. I see in that print, you can see some pretty obvious shirt texture coming thru it.The trick with this I imagine would be to see how "your black" shows up on that particular shirt. Some R&D might be needed before running the order and like someone else said, get approval on it before running some big order.