I suppose you could buy a big Fresnel lens and then cut out a square near the side, and only use that; it would focus the light but also change the angle.
There are flat sheets of prisms, that do what you need there. You probably know them from pictures you had as a child that change what they display depending on the angle you are looking under.
1. heat would be more evenly distributed reducing the need for large heatsinks
2. smaller fresnel lenses could be positioned much closer to the light reducing thickness
3. with a lot of LEDs there'd be a less noticeable grid at the edges of each fresnel lens from chromatic aberration.
I'd totally buy a 'sunlight window' product like this.