study Steve C's prismatic fonts, or others & think of light sources.
The letters above all have some issues with them.
Actually in the OP's case, he can just draw additional vector contours to match his clients artwork, but for creating vector prismatic effects by hand, think of light sources, and picture carving or routing a true incised, or reverse incised (prismatic) letter and then you should be well on your way to identifying where new vectors should be added, and how they should be painted.
Here's a variation I would suggest on the "O" in the above post: