30 direct reports is an astonishing number, and it makes me feel like you're either onto something brilliant or are crazy and this structure is going to crash and burn once things get really complicated and fast-paced. I suppose it depends on how routine a lot of the work is. You'd be spending a minimum of 15 hours a week just on 1:1s, but I could see that being as high as 20 or 30 hours; 15 is already two full days out of the week. That is, unless you just don't do 1:1s at all, which seems incredibly risky long-term.

Given a six-month check-in and annual review once a year for each report, you'd have a total of 60 such events a year, meaning you'd have at least one annual review or six-month check-in every single week. You'd have to keep up with the unique performance characteristics of 30 different people in order to conduct these reviews in any reasonably useful and professional way that actually encourages real growth. If there's any sort of interpersonal conflict or unexpected project complexity, this could easily burn through enough of your time that you'd have to blow off nearly 30 people in the meantime.