Local IBL for EEVEE

I would like to propose a possible implementation of local image based lighting in EEVEE.
Essentially, the idea is this:

Allow the user to use local reflection cubemaps as a source for indirect diffuse lighting. Right now, the sky or irradiance volumes are used as sources for indirect diffuse lighting. Using reflection cubemaps as sources of indirect diffuse lighting as well as indirect specular lighting would would very similar to sky lights - but instead of globally, it works locally.

I believe it fits well within the quick, iterative EEVEE workflow. Together with the superb bent normal ambient occlusion method, I think the results will end up quite convincing.

Ideally, users should be able to choose to use each reflection cubemap (which might need to be renamed to environment cubemap), should selectively be able to affect only reflections (specular) or indirect diffuse lighting. Ideal placement for reflections and diffuse might differ in practice.

Here is a similar implementation in Unreal:

forums.unrealengine.com/development-discussion/rendering/1493669-localized-ibl-implementation