On the other hand, I have 4-5 hours of meetings a day, often in scarce overlap hours between timezones. Having to take 10 different random schedules into account would be hell.

Sure, people could just work flexibly to accommodate the necessary meetings, but I'm my experience, that just leads to people being on call for 10-12 hours a day with no regular schedule.

In every company I have been part of, workers who didn't need dedicated work times simply didn't keep them. It is only becomes an issue if it doesn't work.