1. Skin in the game. Equity, profit sharing, guaranteed monthly bonus based on performance. Doesn't really matter as long as we share. Because if I'm good and work hard, I want to enjoy the results too. A fixed salary is not going to cut it anymore.
2. Freedom over actual implementation and veto power. You may be good at running a company. But I'm great at building things. So when you give me a task, don't tell me how to do it. Yes, we can talk about it and make decisions together. But I must always have the last word. Because, more often than not, I understand things better than everybody else. Including you.
If your lead developer does leave, expect a major slowdown, morale decrease and even further resignations. On paper he might look like a replaceable asset. But your development team doesn't see it that way. We're all humans. And relationships matter.