Keep it simple, stupid. You do not make something that is hard (flying to an asteroid) even harder (flying the asteroid to a location certain the flying to the asteroid).
What a total waste of manpower and time. But it sure succeeds in pushing the manned Mars mission a little further back. Gosh, with all these 10-20 year pushbacks and new "starting point" missions (the moon, asteroid towing, etc), is it outside the realm of of possibility that there might be some native fungi and mosses on Mars, or a very high probability thereof, and that bioethics is a tougher problem to solve than actually flying there?