I'm not saying to replace the current update method. My point is GitHub release can be automated and some plugins already have their releases at GitHub, so I think it will save time and avoid human mistakes(for example: upload wrong file) to add this new feature to calibre plugin server.
Another reason is new accounts of this forum is not allowed to edit their posts. It's impossible for new developers to update their plugins.
And I still think it's need to use the self-signed certificate for
https://code.calibre-ebook.com/plugins.