Well realistically, any bike can be used to tour on. The idea that without certain features a bike is good for no more than 20 miles at a pop is not really rational.

Fender- and rack-mounting is nice, though it is not difficult to find racks that don't require rack bosses.

As long as it fits you, is made of bomb-proof and easily-repaired components, and it's comfortable over long distances, you can tour on anything.

For reference, I tour on a fixed-gear with skinny tires, not a dedicated touring rig per se.