Headerbar / client-side window decorations for the mail composer?

Often I look at the mail composer window and think "this one, more easily than the main Evolution window, could be converted to use a headerbar". It has much less menu items than Evolution's main window, the toolbar doesn't have an option to be turned off, and about half of the menu items are redundant with the toolbars anyway.

The need for it was particularly striking to me today when I used Nautilus' "send to" feature to email a file and Evolution 3.36's composer showed up like this:

Look at that, there's only ⅕ of the window's height left available for the actual content of the email! Well, while the headerbar doesn't solve the space eaten by the infobar (see issue #962), it would help a bit; it would not only make the window look a bit more modern, but also save a bit of precious vertical space—the equivalent of a toolbar's height.

So would this idea be considered? If so, I could make a more precise evaluation/proposal of what to do with its menus.