I suggest that you need to add a very understandable and detailed chapter on
helpdek site, explaining this "new" material approach with comparison to traditional one, and how one should migrate to it, filled with examples and tutorials.
I believe that it would take some effort for a lot of users, who used to classic approach, to start using this new one with the same ease. Currently I can imagine exactly what map should be in reflect, refract, diffuse, translucency, e.t.c. slot, to make material look as intended. This is not the case with PBR material, and you can see it by the questions above, and I believe that here is the progressive part of your audience.
Maybe it would be a good idea to add some script that converts traditional materials to Physical, converting and placing all maps correctly, to achieve correct result. Or may be some map node that would take a traditional diffuse, reflect, refract, translucency and other maps on the input, and generate correct output maps required for PBR, like roughness, metalness and others. This might help with asset migration and migration in general. One could see how new PBR maps should look like, to achieve the same (or close to the same) result as with the classic approach.
Thank you. Hope this make sense.