Not a million flaws...
But one major one. I did a rough calculation once for what how big a sunshade would have to be to permanently hang in the kind of orbit (at the L1 Point) required to stay between the sun and the Earth, and cast any kind of large area of shadow.
Hint: The Moon is almost four times closer than the distance of this orbit, and the penumbra of a solar eclipse (when there is one) maxes out at about 200 miles wide.