Hi @Krzysztof.N and @Daniel_Wright ,
Maybe you have already thought about it, but what about making Lumen work in baked scenarios? Almost any game needs ALL the meshes to be movable, so this could give you (and us) the headroom to gain more performance too. A whole baked scenario qith just a few dinamic objects.
I think Lumen could work just with dynamic meshes + stationary/movable lights only (when static lighting is set to Allowed), instead of throwing tons of rays in all directions, against all actors.
It could be (in my immagination) something like only throwing rays along a radius of action from the light source (like the attenuation distances of every light), and only when a movable actor is detected inside the light frustrum. And, from that certain object, throw the bouncing (maybe just 1 bounce) rays to project GI and/or AO over the neighbour actors (also determined by a radius falloff, for example).