Well, I'm a guy who likes hard problems, so I'd tackle a hard part of the circular economy, probably some kind of marketplace for people to earn money in bitcoin. And not in small/gimmicky ways, on uber or upwork type scale. I'm actually surprised nothing has achieved massive traction in that field yet, maybe bits of financial infrastructure missing. I think stakwork.com are doing great work in that regard but there are also other angles or avenues that should be explored.

Or maybe I'd just do open source work. Lots of opportunities in the Lightning ecosystem, not least once Taro comes out I think it will unleash a massive wave of innovation with plenty of opportunities.