I think you can import/export between bzr and other DCVS like hg, so you could use hg as your local manager and then just push/pull from the remote host.
How do you plan the user interface for it? I thought about an environment which takes the image path as argument and awaits the drawing commands inside it. Could be made aware if it is used inside tikzpicture to create a scope only while it will create an own tikzpicture outside.
@Caramdir: Looks good. I'm planning to allow for different grids in my solution so that it can also print 0-100%. Then your code would only have to use it.
@Caramdir Good idea. I don't think people have something against it. We should of course credit them in the packages.
How are we going to organise this? Should the different answers start in their own files first (unless there are really obvious ones that should go together)?