That is a cool problem. 
I am not doing anything like it but i would love to see the solution for it. I tried to find some but with no results.
One thing i can think of is something like your first idea. But it will take a lot o work if your levels are big.
You can add every light as part of actor and in that actor add the collision sphere and set its radius to the radius of the light so you can get overlap events from it .
As for the shadows, you can manually add some trigger zones in shadows but like i said it will take a lot of work and actually is almost stupid when i think of it. 
Best regards
Kavaar