I would try something different. All supplement stores sell the same stuff which is great, you need some of the big names to draw in customers. USP labs, BSN, etc.
However, I would love to see this in a store. You know how candy stores have the candy islands which are huge bins full of different types of candies, gummy bears, chocolate everything, etc. I would try something similar to that but with different blends of protein, carbs, creatine, BCAA's, etc. A chain of stores located in major metropolitan areas that would appeal to both the average Joe "six pack" and the average anabolicminds reader (I would say usually more of a meat head, muscle freak, (insert other lifting cliche here), that would allow more customization without having to worry about shipping and the hassle of waiting would do rather well.
If you are thinking about starting a supplement shop, please move to DC/Virginia area, as I have not been able to find a decent place around here. All this area has are the average GNC, Vitamin Shoppe, and Vitamin world. --lame.
If anyone knows of a "mom and pop" supplement store in the VA/DC/MD area let me know!
Paul