Here is a scene file which makes cubemap generation (for Unreal) simpler:
CubemapRenderRig.lxo

Just import it to any scene and render the first 6 frames from the CubemapRenderCam camera. The frames should be added in the same order to the Cubemap in UnrealEd.

There is a sphere object as well, around the camera, which blurs the surroundings. The RefractionRoughness parameter in the BlurMaterial group adjusts blurriness.
(At first I tried camera DOF, but that way there were seams between the cubemap’s faces.)