smbwall

[David Brodbeck]

Couldn't you write your own versions of 'shutdown' and 'wall' that are
Samba-aware, and called whatever Samba-wall script you're already using?  In
the case of 'wall' it could just be a wrapper around the existing binary.
shutdown is a slightly more complex problem, but a Perl script that did the
timing and notification, then called the existing shutdown to request an
immediate shutdown when it was done seems like it'd work.