re: Asteroid tug proposal
Sounds like a good investment. Unfortunately, something with commercial use, capable of steering an asteroid full of metals and other goodies into an orbit near Earth,* would require a much larger delta-V capacity. Simply nudging one into a slightly different trajectory is a lot easier.
*The closest I would try to get a mining asteroid to Earth is somewhere in the same orbit the Moon is in, or a distant Lagrangian point. Preferably L4 or L5. In practice, it may end up a hell of a lot cheaper and easier to mine the asteroid on site, and only ship refined materials back.