I may have stumbled upon this int he past, but have since re-discovered it and want to share....
https://warontherocks.com/2020/01/reflections-on-teaching-wargame-design/
It is a nice little blog about professional Wargame Design. There are a lot of great insights and resources on the page.
In this case, "Professional" may mean something a bit different than making money and publishing, but the insights are still fun for us to read about!