This his the nail on the head. You need someone who can turn your vision into reality.

On thing to add is that you need to be very careful about governance. You need to be clear what the COO has authority on, and what they don't. You also need everyone to understand that when the COO speaks, it is as if you are speaking. You can achieve some of this by intelligently designing the reporting relationships. (Did I just advocate intelligent design?) You also have to do it by backing them up. If you give the COO orders, they execute them faithfully, people go around the COO, and then you backtrack, you will kill the COO's credibility.