The only issue with enabling this kind of thing to be set using material parameters is it then makes the shading model twice as expensive, because you’re going to use all the shading models plus a choice between the two diffuse models. It would be nicer if there was a project setting for things like Oren-Nayar, Lambert, Disney, etc including settings for the specular and stuff… But it’s one of those technical features, so I don’t think it should be exposed to people who might not understand what it does. I think at least being able to set it in the USF is something handy to have. Though, I would love for some more shadow filtering settings, shadowmap depth precision settings, and general fixes to how the filtering code works (because right now, the more shadowmap filtering, the worse the depth bias artifacts are, the bias setting should be applied to the filter taps based on the offsets not a global amount :s)
Would kill for shadow filtering like Crysis 1’s, tempted to port it over actually.
As for custom lights, you can do those just fine using bp & material editor.
They use an unlit additive blend mode material which samples the gbuffers (no specular, I want to use these as ambient lights with a custom lighting falloff / calculation like CE has.) Also thinking to add planar area lights as well but obviously those would have specular and fully integrate into the shading pipeline - probably a USF modification and code to support those though. I also want to allow you to add cubemap textures to control their colour (because UE doesn’t support those, optimisations from pre-4.0 I guess, should really be revisited now there’s support for texture arrays…)