actually as far as I know KeyShot just uses matcaps (material captures). Which is rather easy to implement in unreal.
I just posted a thread about it, if you wanted to just create swift KeyShot style renders, I believe it is entirely possible
//edit: on further investigation. I believe it is doable, in conjunction with a library of tileable normals (model would need UVs for that though), you could easily get something similar going.
with a compositing material. I think it would be relatively easy to set up, you could fine tune lighting influence to some degree too, and use tileable scratch maps etc