I'll try my luck with a drilled out pinion, like you said, before I go wrecking the motor or spending more "solid" assets on another motor. I just dont want to have it slightly off center and end up damaging the gearbox somehow. I don't know how, ask Murphy- he knows...
Do you have a drill press? I usally use mine with a 5mm diamter blank and line the pinion up in the vise with that blank, then swap it out for the 6mm drill bit. That way the pinion is correctly lined up with the drill centerline.