It is good to see someone making double-shot PBT keycaps! However, I agree that before going to the trouble and expense of making molds for them, it would be good to conduct a survey to assess interest in specific fonts, point sizes, orientation of legends, and background colors and foreground (legend) colors.
Taking a look at some of the time-honored designs would be helpful, such as the keycap design on the venerable IBM Model M and the classic Cherry font, especially as implemented on the Olivetti and Dolch keyboards.
Regarding colors, because it is not possible to produce dye-sub PBT in a white on black keycap, it would be nice to do white on black double-shot PBT. It would also be good to have two-tone schemes available, such as the classic off-white (ivory) and beige with black legends, as used in classic keyboards such as the IBM Model M.
Thanks.