Supposing you can re-orient parts of the "huge solar sail" then wouldn't it become rather like the sail of a ship or the wing of a plane, and be usable as a control surface for maneuvering?
I'd imagine that in the neighborhood of L1 you would try to find some equilibrium point a little closer in to the sun so that the force of the solar wind matches gravitational pull to the sun. If you start drifting in to the sun, you expose more surface area, and if you're drifting towards the Earth, you re-orient the sail to absorb less solar wind.
