Thank you, this is a good suggestion.
I listened to a replay of your recent presentation for ReSolve, titled "Portfolio optimization when you don't know the future (or the past)". I found it very educational, as it turned a "unknown unknown" into a "known unknown" for me. I had not considered about the impact the uncertainty of historical data has. Your presentation made this very insightful.
However, it did made me wonder: in your first book, Systematic Trading, you explain the handicraft method of first spreading the available account volatility over several asset classes, and then spreading it over several instruments within each class (e.g. chapter eleven). If one uses only a few instruments (e.g. you use three instruments in the presentation and the book) I can understand this approach. However, in "real life" you use much more diversification and probably around 30 ~ 40 instruments. In that case is the cascaded approach converging towards an (1/n) approach, with n being the number of instruments. Each of the instruments will get approximately the same weight percentage, most likely about 3% each.
Add to this the uncertainty of the historical data, and its influence, and it becomes less clear what approach would be the better one: the more complex cascaded approach using correlations and such, or the much simpler (1/n) approach. In your presentation you referred to having had seemingly pointless discussions on whether a portfolio should have "one percent more, or less, of a certain instrument".
Does portfolio optimization still serve a purpose when the number of instruments is large?