I think that this is a much better plan- gives an economic reason to stay, which is going to have a lot more staying power than "because it's there". Although, this is itself rather dangerous since we are then intentionally steering asteroids towards the Earth.
Well, I would imagine we would start with relatively small ones. The cancelled Asteroid Redirect Mission would have targeted one about 25ft in diameter which would be harmless if it ended up in Earth's atmosphere.
