Any way to get the displays menu in the menubar?
You could use a third-party utility named Display Menu. It's available in the App Store for free. I've been using it for quite a while and it has work just fine.

By the way, when I open /System/Library/CoreServices/Menu Extras/Displays.menu it puts the same menu as the [] Show mirroring options in the menu bar when available check box in System Preferences > Displays > Display, does when checked, but does check the box.