As a non-backbone LISTSERV site with a small number of heavy network users,
I think the local systems people would gladly give up some CPU to
LISTSERV for the capability of doing global signoffs.  (I've been asked if it
exists many times.)
 
What if LISTSERV stored all the global signoffs sent during the day and sent
out one DIST job in the wee hours?  I assume that would cut the CPU some and
would lower the number of spool files if a NAD globally signed off a large
number of student accts.
 
If/when such a command is available, I bet the systems folks here would like
to make it a routine part of a killing a userid--irregardless of whether the
user was a "known" network user.  I would expect a lot of use of the command,
so it is in our best interest to make it efficient.