If your work DNS service does not resolve hosts
on the internet (only local to work), some sort of
switching name server needs to be set up... BIND
probably handles this now.

The new IP address at work needs to be such that
machines you want to connect to at work know how
to route packets back. IP masqing may be useful here.
Conceivably one could use a SLIP/PPP emulator (e.g
"slirp") on the work side so no new IP is needed there.

Performance will probably be a bit slower than the
SSH port redirection tricks. It is not clear mounting
files via NFS over even a CM or DSL link is that good
and idea...

Be careful with routing: don't route your company's
traffic out to the Internet via your SSH link! Or otherwise
cause weird routing loops or deadends.