Steve,
With all due respect, your friend is going about this the wrong way. The pro shop design needs to have its size, space and flow planned first, with whatever decorative ambiance he decides on to come later, much as feature design comes after routing.
So, the rustic feel of SH might not work at all in another area. The aesthetics should tie to the course itself. Your preconcieved notions of a "quaint" shop might not be right for him at all. I remember going to NE on a potential project. With me was a Dallas based CH architecture firm. We played golf and talked philosphy for a while. The CH architect kept talking about fabulous "wet areas" he would build him, and I could sense the Owner was getting uneasy, and he dropped some hints, but the architect wouldn't stop. Finally, in NE directness, but also very polite, he told the architect that New Englanders don't parade naked in front of their friends! A few minutes later, he suggested that a Dallas firm probably couldn't understand the regional nature of the design and politely dismissed us both from the project.
As someone pointed out, what kind of course he will have may determine the space needs for merchandise, as will the quality of his logo and overall experience. Very few buy shirts from Tiddly Links Muni, but many buy if the course is an overall great experience.
From hanging around many pro shops and looking at it from an operators perspective, I can tell you most think they got shortchanged on actual counter space (even if old shops also have limited space) as well as office and storage space. New ADA laws also mean you can't store stuff upstairs w/o an elevator, as a wheelchair bound employee couldn't fulfill his/her needs to get new merchandise down.
Design is also affected by the type of off season, if any. Some places like to be able to downsize to one person, which means centralizing the food and shop operations in the center. Where there is no off season, vision to the first tee is usally the primary determinant of where to locate the pro shop.
So, a lot of things go into the design before you try to replicate the aesthetics of another place.