I think there should be a option (ACP level) to show as "Main Calendar" (the first that appears once clicking on calendar) a Calendar that includes events from ALL calendars in one place.

Then of course you would be able to "filter" events by selecting the specific calendars, just like it is now.

the way we have tackled this is to add a sidebar to the calendar page and add an ipcontent calendar feed block from ip content.

but that's only half of it ... the other absolutely indispensable part of the forumla is Marcher's Enhanced Calendar List View which he totally tweaked to work with a sidebar soo

end result:

click on primary navigation calendar tab; see first calendar that you think is most important which may or may not have any events ... but the sidebar shows ALL events up to the # you specify and click on one, takes you to that calendar, be it calendar #3 and there with Marcher's app, you see 5 events laid out in List View

beyond sweet!

Can I see it working on your site suferboy.