A nice feature that Wordpress has is the option to download and install plugins directly through the admin panel, without having to use FTP at all. Also, it would be a great way to streamline updates (both core and extensions).
A worthy note: Wordpess uses FTP/SFTP to update core and plugin files. This way "chmod 777" security problem is avoided. I think FTP/SFTP-based operations is a must, this means installer module would need this too.
Honestly I don't think this can be achieved by 1.0, this also means rebuilding the extensions repository to be downloadable in a certain way.
I think this would require hosting the downloads and standardized upload/format properly etc.
I think this decision is undoubtedly a plus for users who may want to go to Cotonti with Wordpress
I don't think this is doable by 1.0, clearing the milestone for now.