This depends on what you're optimizing for. If you are optimizing for total energy captured per square metre, then you're right about the benches.

But suppose you have a sufficient flux even with some areas being covered so you aren't bothered by the shadows. Wouldn't it be aesthetically superior to have uniform tile types? Or would you prefer they micromanage the tile placement such that the tiles below the bench shadows are different?

Anyway, I think it is a good idea. Better than the silly solar roadways crap.