... the best thing is probably: have the remote have her/his laptop
(gateway 2000 will do already) and do dial-up to a 1-800 number with
ppp. The remote is integrated into the Kingdom, and runs encrypted,
can use public terminal servers (e.g., ANSRemote dial up service for
$35/month+8.50/h connect). Any customer will let you hook up a PC to
a phone line and dial an 800 number.
I would share the concerns of requesting/letting hook up a machine
to a network, already the addressing is an issue, as well as
routing. Not everybody has a guest network outside the firewall to
allow for guests to hook up to their home base.
... and to who believes in letting a visitor connecting a machine to
the LAN: if I know how to write drivers, others know far better. And a driver
can very well have background activities spoofing everything,
tracking tcp connections, watch for SYN and follow tcp option
negotioation until the magic characters pass by.
In my world: only outside of the firewall. I like visitors, but I
don't share my bed.