Currently, "ToonTransparent" and "ToonFade" fall back to "Unlit/Transparent", which looks strange because no lighting is applied. Therefore, I think we need a transparent shader that is lit in the same way as "Toon" and "ToonCutout". Since transparent shaders are often used for hair and costumes, it would be nice if the "_ZWrite" property could be copied, but the RenderQueue should be carefully considered as it can cause rendering bugs.
Here is an example of the transparent toon shader.