How to get the Toon Shader's outline to display correctly through transmission?

[soeucoisa]

Hello,

I recently did a scene using the Toon shader, and faced an unexpected behaviour of the outlines display:

Here are two spheres with the same Toon shader. In all images, the base, specular and outline are white and set to 1; The Energy conserving check is on and the direct diffuse and specular are set to 1; and the transmission is white and IOR 1. The only differences are the transmission levels.

1 - Transmission "1". As expected, the spheres "core" is fully transparent and the white outline shows fully. Everything as expected.

2 - Transmission "0.5". The spheres are semi-translucent and the outline is darkened. Looks ok as well.

3 - Transmission "0.01". Not good at all. The outline should be nearly invisible, but instead it becomes almost black and very, very contrasted

4 - How, in my opinion, the outline should look. The outline is barely visible, but retains its color (this was done by merging the previous image with a render in which the outline had .01 opacity).

So, is there a way to make the outlines display correctly?

Thanks in advance for any answers.