I am planning to add an external face plate to the skate frames. It would attach to the outside of the frame and be removable. Its primary purpose is be a light diffuser for the RGB LEDs, but also protect the electronics from dirt and debris. My tolerances on the initial working prototype will be kind of loose, as I really just want to get out and skate with them to see how they'll hold up to some mild abuse.

I was initially going to take some photos from above, adjust for lens skew, and outline the shape in Inkscape. So I could then extrude it in CAD and print a first iteration.

Fortunately for me, I attended a local 3D print meetup and met someone who was showing off his 3D printed scanning table that he was using with his Creality RaptorX scanner. I hadn't considered 3D scanning, since my past experiences with scan quality were poor. I thought the reflective metal surface and anodization on the aluminum skate frames would be too much of challenge. But apparently these newer scanners are much better, as the scan quality was quite good and dimensionally accurate. It took a little effort to line up the point clouds from two separate scans and remove the noise, but the STL the software output was very good. 

I decimated the model a bit further in MeshLab so I could import it into TinkerCAD that has a file size limit. 

Since the dimensions of the frame are a bit larger than my 3D printers bed, I'm planning to go to my local library to print it. Most of the libraries in my area now have a Bambu Carbon X1 printers, so the print will fit on the large build plate diagonally, allowing me to print it as a single solid piece.