I think we're talking of the same thing: to have a MASTER calendar that is the result of MIX-IN with other calendars.
Now, what YOU suggest is that I create those sub-calendars and share them with others with edit rights. What I suggest is that OTHERS create their calendars and share them with me with "read-only" rights. Do you follow me?
I may be tempted, as the person responsible for the master calendar, to require rights to those shared calendars that belongs to others and that I want to mix-in, but WHY could I not MIX-IN FOR PUBLISH purpose a shared calendar with "read-only" rights?
This possibility gives responsibilities to the others: if activities are NOT there in the main calendar, it's THEIR problem, not mine 🙂
Is it possible to TRANSFER CALENDARS FROM ONE ACCOUNT TO THE OTHER?
Regarding your suggestion of "(we recommended) having an admin account that is used just for calendar creation, publishing and sharing and not for actual data entry", I came exactly to that conclusion, but since I've done it the opposite way, I'm stuck with all my created calendars in the wrong account (actually in my personal E-Mail account instead of my office E-Mail account).
But still, after thinking twice to this idea, I'm becoming more convinced that it would be better for me to create those MIX-IN calendars myself AND share them with edit rights to others ... yap, this is better. Good sharing on this one.