I don’t see why it wouldn’t work from a technical point of view. Artistically it might be hard to combine the two in the sense that flat continuous toon shaded surfaces would probably make it harder to hide lighting artifacts and thus require very high vxgi settings to get nice and smooth results.
To combine them it’s probably easiest to start with the vxgi branch, as their changes are much more extensive and then integrate the toon shading changes into your own custom branch.