If someone ported diskutility over it would be possible to repartition the phone but not advisable, for two reasons:
1. We do not know if these are REAL partitions that can be changed, or if it's something hardcoded into the hardware
2. This could be dangerous for firmware updates, etc. they might brick the phone, in a bad way.
...However there is a way to get more space for apps, though it is a hack.
First you need to edit /etc/fstab so and take the noexec out of the options for the /private/var partition, so that files can be executable on that partition, then ssh into the phone and do something like this:
mkdir ~/extra_space
mv /Applications ~/extra_space
ln -s /private/var/root/extra_space/Applications /Applications
Now all your Applications will exist in the 7.5gb partition.
Note: I have not tried this on an iPhone and thus cannot guarantee it will work, however, being a true Darwin installation, it SHOULD work because of the way that Unix systems work. You can also play it safe by moving individual applications over and creating symlinks for them. just keep in mind symlinks will take up 1 block of space each, that's usually from 1-4k depending on the inode size the fs was formatted with. not a big deal but just something to keep in mind, just coz it says 0 bytes in the file listing doesn't mean it doesn't use up space =)
This is a simple workaround for running out of space that's used a lot in the Unix world, or at least, I have used it a lot in the past
now of course i'm not sure if /Applications is where everything is put or what, but it will at least help the situation. The lack of "du" has made it difficult to easily assertain exactly where all the space is being used up on the phone.
Perhaps my first toolchain project will be porting du as that is an immensely useful command.
Edit: one of the biggest uses of space is stuff like Perl, Python etc. I am not sure where Python is installed but Perl is installed in /opt . if you move /opt to somewhere in /private/var and then symlink it to /opt, and do the same for /usr/local (IF python is installed there) then it will free up a HUGE chunk of space on the smaller system partition.