So you'd be able to invite everyone in a comm to an event, or invite an on-fly-list, or a custom access group that you have set up? Or would each community have a calendar, and members would see community events on their calendar?

If every calendar has a list of people with defined rights, would this be updated automatically if you give someone new permissions in the community (e.g. posting access) or would it be separate? Would "editing the calendar" be a new level between posting access and moderator?

Would it be easy to allow all your access list to see your calendar but no-one else, or all of a custom access group but no-one else, and have it update automatically when that access group changes?