i for one am going to download interesting packages with w3mir (extras* repository) respectively Pali's download.sh or his improvement on apt-mirror for NOKIA's repositories.
once this is done i will see into porting dpkg-scanpackages respectively dpkg-scansources to Fremantle so that everyone can create her or his own local repository.
without games & themes the whole thing comes down to 15GB.
any mSDHC 32GB card (preferably formatted ext2) can then serve as a "repository" to every N900 owner.

EDIT: sorry, forget about dpkg-scansources
the 15GBs are only armel deb packages, thus dpkg-scanpackages is all that's needed.
i do appreciate that this community is about developing software, but past 31st of December...