Its not as easy cause depth is applied on a pixel dependent on the depth of that pixel while having only one focus point.
For light you would need to apply light on a pixel dependent on the depth of a pixel that is source of that light while having an arbitrary number of possible light sources.
I thought about something similar once to fake global illumination but that requires a smart algorithm to think of first
What should be possible though is applying the AL algo only on a certain (soft) depth threshold. That way you could limit the effect to only the background. Not sure though if that is what you want.