2: It's not a matter of having something waiting to go. The object would have to be extremely close and therefore astronomically lucky, to the probe, and even then all that could be done is a flyby (or impact) as again, right now anyway, there's nothing that can match that kind of velocity, though there ideas from them. Oumuamua is flying along at the speed of what we might produce ourselves if we were to go all in on an unmanned star probe , and we don't yet have our own unmanned star probe to catch it.
Karen Meech seemed to have the same idea of a drone waiting at L5 or someplace. Maybe a swarm is needed at multiple wait points.
Anyway, as i said earlier the feasibility will have to be calculated and not dismissed out of hand. It's just an idea. Better to have something than nothing.