Keeping cluster updated
Using Jamroom
I actually have a cloud module in development (Cloud Admin) that is designed to help with this. Basically as you add servers to your cluster, you add the new servers in to the Cloud Admin module servers tool. It will then allow you to "see" your cluster at a glance, and has some health checks, etc. It also will allow you to run a marketplace update for any server in your cluster - this allows you to (for example) update just one of your front end servers, monitor it, and if it looks good then you can update the rest - without leaving the module.
It's something that is being worked on so hopefully I can finish that up soon - I've had some other higher priority work come in that I've been working on in regards to hosting.
As for setting up your own marketplace, we might be able to do that - basically we would setup your account like a 3rd party developer, and you would create a new private channel that you would configure on each server. Then, when you have a new update (say a skin update or whatever), you would upload the new skin to the system here, and in turn each server that is subscribed to your private channel would "see" the update and the update could be run for it.
Hope this helps!