What type of business would you want to be in if you had no bounds? Expertise is certainly a factor, but assuming you had the resources to hire a fantastic team and the finances to acquire (or start) any type of business, what type of business would you want?
I would create the best geo-targeted group blog for a specific large metro. (And then roll them out across the country or even around the world.) What most businesses need is a way to reach their local target audience. When you create the very best local site that can be grown organically offline and on, you can deliver that target audience. (Think of an expanded version of the "what's happening" column local newspapers used to run on Fridays.) Develop a curriculum to have students (high school, college, even junior high) create unique content. For example, have each one write about their favorite thing to do in town, add a photo and contact info. Or their favorite restaurant and what they eat there. Again, all you need are a couple paragraphs, a photo and contact info. Have the car happy go find their dream auto, take a photo, write up the specs, add a photo and contact info. When their fellow students read what they've written, they'll get together to go out to eat, or for entertainment. Students can create jobs for themselves. The local car lots and dealerships they feature will want ad space to swap in their latest deal or the next car they want to feature. Create ad space right on the page where the new content appears and let them manage it. (The ideal way to let ad buyers manage their own ads exists today, but they are threatening to shut it down. Someone really needs to buy it and keep it running.) Many will not want to manage their own ads so they can pay the students to do it. When the site makes money, the best students can stay - having created their own paying work. Don't make the mistake that local papers are making that makes them obsolete. They want to get paid and THEN they'll cover you. You want to cover the best small businesses up front. Use students managed by an experienced blogger (or team of bloggers) to create interesting content. Get locals interacting on the site. Deliver the audience businesses want and they will be willing to spend money to advertise with you. Do this in one metro and then roll it out in additional metros using one or more experienced blog managers local to each location you add. When you grow your business locally, you don't have to worry about the next Google Panda, Penguin or other black and white end to your traffic. It won't even matter if the lights go out or the Internet as we know it ceases to exist. You will have a community business that can continue online or off. The cost to do this is minimal. The expertise is widely available. 80+ experienced bloggers are already connected in our Blogger Mastermind group and at least one of them is a college educator. She and I have been planning this for years, but the third partner who had the ability to host and do the programming became unavailable. I have additional information written up on this, but I don't know if links work in answers here or not. Contact me for links or additional information. I would love to see this idea take off.
With everyone wanting to know everything about everyone, privacy will be on the forefront of tech and manufacturing-based commerce.
Make me secure and I'll buy.
I think it is very important to keep in mind that technology rules them all. Starting from small to enterprise business everyone is using technology to gain competitive advantage.
I would create the next blogging/e-commerce platform as these are very successful, see https://ghost.org.
I would look at how you add value to people and what do you enjoy. My new business is based on my passions of fishing and coaching people. I believe there will be more small businesses started in the next decade due to the change in way people want to do business.
With all the resources and connections necessary to make a big splash in any field? Well, then, I'd aim for something completely unprofitable.
But, of course, philanthropy can be ruled out. You'll want something with a high ROI, obviously -- but also exciting enough to justify 20 years of work.
Compared to 20 years of a person's life, the marginal dollar difference between Profit A and Profit B recedes to insignificance. Plenty of sectors can deliver a high ROI. Yet anybody with a soul -- yourself included -- will choose a field based on how much long-term interest it holds. And that's a personal, even idiosyncratic choice. No "expert" can advise you.
So I'm guessing you're essentially asking what sectors interest other people -- sectors, that is, with realistic space for profitable growth.
For me personally those areas would include publishing ventures and innovations for the digital property market.
But if I were a realtor, then I'd say real estate, wouldn't I? And if I were an app designer, then I'd say to you: "Apps, apps, apps, apps, apps". And so forth.
Apologies for the essay!