Like 12.21.2012, it's not the supposed incident that concerns me, but the panicky sheeple that whip themselves into a frenzy over the impending catastrophe. If they ever announced an impact, or even a high possibility, people would turn into even bigger idiots.
"Paint it" option...I can see the physics of this method but if we can get to it close enough to paint it why not destroy it?
"Can't build a spaceship in time because it would take 2 years." I'm assuming they are only considering having it made in the USA with all the current bureaucratic and permitting processes in place. We would still be "ramping up" for WW2 if we had the same environment then as we do now. If we considered only real world/ physical factors, I'm sure it could get done. If you factor in all the politics, permitting, approvals, and politicians wanting to make sure they get credit or have deniability then yeah, it will take years.
Why don't we send Justin Beiber up in a spaceship with a PA system and let him sing to it. That should either make it implode or turn around and go the other way.