Something I think would be really handy would be an updater. Perhaps something like Windows Update. As to the repository, maybe you could use the CVS or something - like Debian unstable.
The state that Haiku is currently in, if someone who cares to code an updater app does, couldn't they use a generic user/pass to log into CVS and grab all the changes? I'm not certain how CVS works, but think of it as automating the process.