Hmmm.. this is an interesting concept, it would make for some stunning diversity of plants in a tank.
When you consider a bank of VHO T5 lights over a tank, it gives you a flat, uniform spread of light.
I think the 'spotlight' method would give you a more visually interesting tank, that has light and dark areas, and would get you away from the brightly lit 'box' type look of VHO lighting.
It would be like running banks of fluorescent lights in your lounge that replicate daylight throughout the entire room, rather than a lower amount of light that highlights specific areas of interest.