One thing you need to come to grips is that regardless of how smart you are, the VP of engineering is probably someone that has a lot more experience and clout than you do. If they aren't, then the senior management of the company is terrible. If your company has grown to the size of 40-50 people, that's the time when they need real experience to help drive them forward. They can't take a chance on a great programmer…
Why is it acceptable for the Founder/CEO to continue leading the company at 40+ employees but not acceptable for the engineer to lead an engineering team at 40+ employees? Seems like a double standard.
However, for all other roles in the company, the important thing is having the experience to scale and lead that part of the company: sales, marketing, product, support, engineering. When the company is young, those roles will be filled by allrounders: people a few years experience who do everything in that area. As the company grows, you'll want to hire VPs who have the skills to lead those areas, often people with >15 years experience as a practitioner and/or leader in those areas.
It's not just engineering: you want a VP of Sales, a VP of marketing, a VP of product, etc. Those people will have the skills to take your existing sales/marketing/product/engineering org, and scale it without damaging it. If you have that skillset in your engineer #2, than it would make sense for them to do that role, but it's unlikely that they do, and certainly doesn't seem like it in th OP's case.