No better light than the sun itself, right...?

Alright. So we all know that the sun is the best light, right? Well I have an idea ... how about a hybrid grow box? A normal grow box as usual, but in place of the lights, put a skylight at the top. Not a window, mind you, that's just a green house. I mean one of those kickass skylights that intensify and magnify the light before comes out. Put that kinda far from the plants, and then mylar all around ... any opinions? Anybody think it won't work? Just a thought.