Would a slightly conical mirror with its apex pointed towards the laser be self-stabilizing in tilt? Kind of like an aircraft with dihedral wings [1] is self-stabilizing in roll - imagine the laser illumination as an analog of the aero lift vector on the wings. If it tilts wrt the laser, the asymmetric illuminated area should counter the tilt.

[1] https://en.wikipedia.org/wiki/Dihedral_(aeronautics)

> Spheres would cause a major issue - the laser would need to strike the centre of the circular visible surface.

> Otherwise you'd end up with the light bouncing of at angles other than pi, which would direct the probe to the side.

No, because these lasers won't be focused to a point smaller than the size of the satellite. I'm not sure what the waist will be, but presumably it's much larger than the mirror.

The real reason these are sails is because they maximize the momentum transfer per unit mass. But unlike sails on boats, this force can't be transmitted to a displaced payload using tethers/struts, so the payload must be dispersed and integrated within the sail itself.