Not only do I think it's possible to stay involved in engineering/design work, I think it's optimal, at least for the first few years. The best technical CEOs do this--they're happy to hand off most of the organization to a COO, but not product or engineering. Mark Zuckerberg did this for a long time at Facebook, and probably still does. Every time I meet with Elon Musk I'm struck by how much of the conversation is about engineering details of SpaceX or Tesla.