I suppose it depends on what you want to consider a cubemap, but lumen actually does support something quite similar to what I believe you’re elaborating on, if I understand correctly.
To support lumen distant lighting, it has a series of world-space probes that cache distant dynamic lighting to keep the cost low where the scene doesn’t need to be too dynamic. If you switch your PPV’s reflection method to ‘screen space’, it does something rather clever: it enables SSR, but uses those world-space probes as an automatic fallback. Should an SSR ray miss, it will sample from the nearest probe; while the probes are significantly lower res than the average cubemap, they’re generally good enough for rougher diffuse lighting.
I haven’t played around with it too much, but I know there are ways to increase the resolution of the radiance cache probes, so you may be able to actually extract quite good reflections out of them.