Is it possible to set up a single-interface IPNat box??

A friend of mine has a need to set up a home network and the box he procured
to do NAT currently only has one NIC.  What we were thinking is:

                                        (The Net)
                                            |
 (inside host)        (NAT box)    (router to outside)
      |                    |                |
      \--------------------|----------------/

Where inside host is assigned a non-routable address, the NAT box has a "real"
IP address on the interface and an alias that is also a non-routable address.

Inside host default gateway == non-routable address of NAT box
NAT box default gateway == router

Getting another NIC obviously isn't a horrendous expense in this day and age,
but I'm curious whether the above setup should work (in theory or in practice).
I haven't looked at the IPFilter documentation enough to determine whether 
we were both crazy or not.

Any comments appreciated (other than comments on our sanity.. We know we're
crazy 8-)

--rafal

----
Rafal Boni                                                rkboni@concentric.net