The first part of your comment is valid no matter if it is Cockpit or any other UI.
Even with Nethgui this is valid.
As a general rule. Exposing the adm interface to WAN side of the server is not a smart move.
Regarding the second part of your comment. I suppose that Cockpit will have native support for management and not depend on the e-smith layer.
But also for specific parts you should use / develop your own modules, since Cockpit is not going to interact universaly with the system.
For this part of development, it will be great to have a “insider” view of how it can be done by users willing to start playing with the code.
So i guess it is a good starting point for the new UI to have it “presented” alongside with the actual implementation in the NS environment.