Leave $HOME as set. For AIX currently /.
To avoid errors like rm [-rf] * in the wrong
directory, the location of roots $HOME is not
a real help (all those who removed libc.a know).
Set as least an alias rm = '/usr/bin/rm -i' or
better define an rm function which does some
checking and if -R/-r are used or the command
is executed in a system dir or ... add at least
the -i flag, print an additional warning, etc.
For core files filling up /
mkdir /core
or see the syscorepath command.
If you don't like smit.* filling up / create symlinks
to another dir, like /var/root

I expect IBM testing is done with $HOME for root
at the default. They will not catch errors in the
tests like
- on SP2, Estart failed to start the switch
In one perl script executed on the switch primary
node was a series of command|command|... and one
commands was usr/bin/grep. Works fine if home is /
but fails if home is /root, /home/root, ... :-(
- update_all failing to update an X11 package leaving
a broken installation (fixed by reinstalling the package).
Same as on the SP, some re/post install script was looking
for usr/lpp/X11/something
- other errors?