In alternative we could develop a patch that forces menus in the hamburgers to also show in the menubar. But I don’t know if it’s feasible.
Any modification that you create from outside an application is called a hack and also even when technically is possible, made this is really complex and your code can be break in any update of the upstream app. Also the change can not be general, because all applications have a different set of actions. This is not at same as how gtk3-nocsd work and how is implemented the unity-gtk-module and his appmenu-gtk-module fork of the vala-panel project (where i’m a developer), because what that projects are doing, is the same to all applications.
Any way, I was trying to make this possible, but at same time the Gtk developers was working to prevent that this will be possible. The result was i lost the interest on make it. It’s to much of work make it with the Gtk developers help and try to make it working against hims, is really almost impossible.