Hey, that's what our NYIF looks like, only it's light grey! And of course copper.
Wouldn't the voltage drop be a problem anyway with such thin wires? How long do you plan on making those runs?
Steel wire definitely isn't a good idea. I read somewhere about a trolley bus service in Vienna (1940ies), they fed 750V into the wire and on the other end they had about 300... with only 1 bus... the service never opened to the public.
