That's a tricky machine from looking at it. The CPU will run m0n0 no
problem (it's the same CPU that you'll find in things like the Nokia IP110).
The fact that it requires soldering to get a serial port or VGA connection
is bad. The specifications seem to indicate it's a 16MB disk-on-chip vs
32MB, but both are plenty for the current versions of m0n0wall.
I'd also be concerned about the fact that the slot is an ISA slot; ISA
throughput is limited to about 4mbit in real-world applications.
At a glance, I'd say that the hardware modifications necessary to install
and run m0n0 are probably not worth the effort. Which is too bad; it's a
nice little box.