The wordpress team distributes WordPress updates very often, the process is very simple, you unzip, FTP (upload) the update, and you are done.
I do this very often for many many websites, although the process is simple, it is time consuming, the reson is that on shared hosting, i can not upload a zip file, i have to upload 800+ files for every single website, the latency of uploading 800 * 10 files adds up, and i should not need to do this
the task look as simple as, create a system to upload the new version to all FTP destinations every time there is a new wordpress update.
This is also more secure than allowing wordpress to update itself, wordpress code files should not be writable to the web server, only to the FTP user.
Anyway, i will get to this project soon (Maybe it will take 10 hours work), and once done i will keep you posted on how to add your FTP details.
Till then, happy wordpressing