You need a COO and if you can afford one, you should hire one. What you appear to want to do, set the strategic vision and lead the team, is exactly what a CEO does. A COO makes sure that vision is executed on a DAILY basis and that's what you want. A good COO is a beautiful thing for a scaling business, go find one!
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.
Good advice. This will be tricky as there isn't a massively rigid structure in place as it is. It's like that that the COO will be asking me to do things at times, so governance groundrules will be very useful. Reminds me of http://holacracy.org/
IMO I'd start the role as Operations Manager or Director of Operations and grow it from there with the company. Lets you get someone for cheaper who can hopefully grow into the role as the company grows. It doesn't sound like you need a full-fledged COO yet anyway.
