Rondo, wants a pretty classic design that is hard to go wrong with. I was talking more about an off the wall body design that a customer may cook up. I've been there on an early build, it was an upside down Jazz shape that the customer was extremely excited about. After playing it for a while he was asking me to build him another body for it. Even letting a customer use your mule to test pickup placement isn't a guarantee. They may choose an extreme bridge or neck position that they love in their bedroom, but hate in a band mix. Part of being the builder is letting them know what works well and what doesn't work so well. You just have to be careful I guess, one bad design, customer inspired or otherwise can devalue your brand.
I'm sure you point out anything that is an obvious design mistake, I was just pointing out that its a pretty fine line that is easy to fall to one side or the other. Giving a customer too much input, or not giving them enough are both not ideal situations to be in. I personally will take their ideas and come up with a 2D CAD drawing and finalize it before any sawdust is made. I would prefer to use one of my proven designs though, and let the customer choose the electronics and finish.