Re: Drag
The gyroscopes can maintain the angular orientation of the satellite. However, this (giant) mirror will still act as a solar sail - radiation pressure from reflection - https://en.wikipedia.org/wiki/Radiation_pressure
So what happens to that radiation pressure? In order for the satellite to remain in its orbit, something has to counteract it. The maximum radiation pressure would presumably be 9.08N (see link above) per square kilometer of mirror, although in reality it would presumably be somewhat less depending on the angle of the mirror to the sun. Not an insignificant amount of force to counter, particularly given its continuous nature, and it will have to be countered.