@BlackJack: I think your project's visuals would heavily benefit from using reflections, on most of the materials. Cubemap and maybe even screen space reflections (a combination of both approaches usually gives best results). Additionally, you could do a view space normal lookup highlight/ shading thingy for at least metallic and skin materials.
I don't read too many tech papers but I found
http://www.adriancourreges.com/blog/2016/09/09/doom-2016-graphics-study/
and a Killzone: Shadow Fall paper very interesting and inspiring in that regard.
The metal highlight or skin lighting is as simple as
OutLookup = mul(normalize(mul(InNormal, matWorld)),matView)*0.5+0.5;
in a vertex shader, with an appropriate sphere-ish texture. They used that for instance for character rendering in Half Life 2, if I'm not mistaken.