Well if it's .030 or so, then piano wire comes in .032, and other sizes. It has some carbon in it to harden, so the resistance is a little higher than mig wire I think -- resistance would be a good thing -- it will provide more heat with less amps. The big problem with thick wire is too low a resistance and too high an amp range.

Stainless wire is usually even a little higher in resistance than carbon steel. I have used solid stainless fishing leader (single strand) for my hot wire bow -- but I went with as thin a gauge as I could find for a thin cut, and low amp draw (I think it's .018"). Maybe leader material in heavier weight would work well for this.

One thing I forgot to point out -- this lathe will still only make a shape of rotation -- not a flattened side shape. If you think of the Gee Bee, the nose section is circular, but the tail section is flattened. Most planes are that way, more or less -- you can't do an oval section, only circular with the lathe

The only way I know of to do a true compound fuselage shape in a solid foam construction is the profile and top view cutout, then trim and round corners as required.

There are many built-up methods for complex shapes -- but not many solid carving ones.