all of your suggestions completely undermine the purpose and simplicity the ossc delivers.
Depends on your point of view, I suppose. To me, adding RF, composite, and S-Video would undermine the simplicity of the OSSC as it exists now. Integrating those additional formats would require a redesign (likely a new, larger FPGA, and more complicated software), and that would do nothing for existing OSSC owners.
A standalone decoder would work for all existing OSSC owners, and it would have purpose beyond just the OSSC, such as letting people like me connect S-Video sources to their recent TVs that have YPbPr but lack S-Video.
And besides; since RF and composite are so heavily degraded to begin with (S-Video is actually pretty fine), something like this would only be a stopgap for most interested people–to hold them over until they can get an RGB or HDMI mod installed.
As for the rest of my post, I wasn’t attempting to suggest alternatives; rather I was trying to illustrate the less-than-desirable hoops that we currently have to go through to connect our legacy consoles to modern displays.