Yes we are aware of the old and insecure nature of rexec, but our server-side is SCO unix and sadly does not support any SSH.
The server runs some old software and drivers that are not ported to linux or other O/S of choice, probably never will be ported as the engineering cost is too high.
So we have a need for rexec (we think)
Also we will be running this on a fully private network (not over the web), and so security is of less concern