Things like these auto sort themselves out - if the meeting is ""Weekly HR thing that HR spams everyone with but nobody attends and doesn't matter anyway", then nobody that has actual work to do attends, and they don't accept the meeting into their calendars. Its not like somebody would count attendance on those.

Critical stuff shouldn't get a reaction like "gee, he has something in his calendar, well we just skip this 10 mil deal because disturbing him is a no-no and he would be mean to us". Critical stuff is critical, take people out of their meetings, life is about priorities.

But I understand the appeal to control freaks out there, everything is plain and visible (or not, depends how you set it up)