Screen printing one shirt is very expensive and impractical at remotely reasonable prices. I'm very interested in the concept and I'm looking forward to seeing more. Not sure if you've looked into it, but CAD-cut heat transfer vinyl can emulate a screen print pretty convincingly and comes in a plethora of colors. Would definitely suit the one-off nature and for a period of time it is what Spreadshirt (and others) were using when people ordered low quantities of simple designs.