IMG_0004 by
AviationMetalSmith, on Flickr
The problem , if you analyze it, (and I have analyzed it), is that the manufacturers are building and selling "carbon copies" of the traditional CrMo Steel Bikes. Not too good an idea, The materials are completely different.
IMHO, a Carbon Fiber Bicycle should be more like a Fiberglass Bicycle. Glass Fiber and Carbon Fiber are worked in a similar way. The overall Tubing Diameter should be larger than what would be used in a Steel Bicycle.
Maybe the problem is a lack of Fiberglass Bicycles to base the design on? There are the Bowden Spacelander, of which only 522 examples were built, and the Fiberglass Ladies Bicycle (pictured above), which is very rare, I built one and Robert Egger built one, and I don't know of any Fiberglass Ladies Bicycles except those two.
That's the answer , base the design on a Fiberglass Bicycle. You'll just have to learn to live with the Futuristic Styling, which is inherent in a good design.