Egoshin,
This thread is very interesting and if all works as targeted, an awesome step forward for all n900 users. Power to the people and many thanks for offering your time and energy for all to benefit.
With regards to the moveroot.sh file I had previously used this chasing rootfs space and found this always resorted to hiccups with the desktop freezing, not loading icons etc I think it is due to the relocation of icons & themes, but that's another issue.
I have tried a few things, though blindly I must say, as like a few of us on here, computer illiterate. So I have changed these four items (see below) and suspect running your script with these mods already done will result in similar headaches as the moveroot.sh users, could you please confirm?

mv /usr/share/nokia-maps /home/opt/
ln -s /home/opt/nokia-maps /usr/share/nokia-maps

mv /usr/share/microb-engine /home/opt
ln -s /home/opt/microb-engine /usr/share/microb-engine

mv /usr/share/tutorial-applet /home/opt
ln -s /home/opt/tutorial-applet /usr/share/tutorial-applet

mv /usr/share/locale /opt
ln -s /opt/locale /usr/share/locale


Q1. If these mods will effect the functioning of your script, are they reversible or a flashing in order?
Q2. If reversible, is it as simple as doing the reverse eg:
mv /home/opt /usr/share/nokia-maps/
ln -s /usr/share/nokia-maps /home/opt/nokia-maps
Q3. The script, if any errors or problems, not happy, for whatever reason, can it be reversed or fixed with a flashing?