Calendar Selector - Enable Add to Top Menu as Custom Button

It would be very useful to enable the calendar selector to be a custom button/popup on the top menu (per below screenshot) without needing a mashup.

Right now, one can add a custom button, but non of the actions enable popping up an object, particularly the Vizlib calendar.  

The selected dates are such a critical piece of information - so selecting them and viewing the date range should be easy and prominent.

Enabling the calendar to appear on the menu will save space on the sheet and also avoid burying the calendar on the slide out side menu.   

I think you would mainly need to add an action that enables a calendar popup and then the display of the date range in the button.