First off... I don't even know if what I want is going to be possible yet, so if not I'd still be ahppy to hear that.
What I've been asked to do is create a set of themes for a client, and part of the deal is that I do updates to the themes as they are requested (at an extra charge). The problem that I'm facing is that the client wants the themes to use the standard WordPress update system, but doesn't want the themes to be publicly available.
From what I can see so far, the update system works with the WordPress servers, so in order for the automatic updates to work, I would need to have the themes hosting on the WordPress site, and have them be publicly available.
Is there a way that I can set my themes to be updated from our server or i sthis just not possible?