After read the Ubisoft doc about the Far Cry 4 http://www.gdcvault.com/play/1022235/Rendering-the-World-of-Far i see some interesting things, UE4 need.
For example the anisotropy materials will be nice addition + if give to the artist the option to setup the SSR throw materials (something like a lerp from 0.0 to 1.0 for less or more visibility, here is the metallic & roughness but i speak about other option to manage the SSR) and will be nice add something to manage the distances and angles of the reflections & SSR over the project settings.
Vegetation LODs & imposters, from the 4.3 release UE4 have this Render to Texture Blueprint: Render 3D Imposter Sprites: Unreal Engine 4.3 Release Notes | Unreal Engine Documentation will be nice to give to this the option of use as LOD or imposters for the 3D models LODs (for trees or for others things). (Plus Far Cry use non plane imposters, giving more or less the 3D form in a plane of the real 3D model)
The manage of the light + shadows & sky + cubemaps (see pdf)
The antialiasing changes.
*Question how select in the materials between Alpha Test & Alpha Blending ?