> You make a big ring (roughly of the same area of the spot you are trying to make on the ground)

Unfortunately, this is not how the size of the spot on the ground is decided. Sunlight, even if reflected by a perfectly shaped mirror, spreads by approx 1 meter every hundred meters. At the "edge of space" at 100km, your spot already has a 1km diameter, in reality with a higher orbit and imperfect mirror & tracking it will be much larger. The size of your (ideal) mirror decides the brightness of the spot, not the size of the spot.

Liquid mirrors in space seem like a cool concept though!