It's interesting to observe the assumptions we make about
* 1/8" stainless aircraft cable breaking strength is similar
to that of 1/2" braided dacron. It's also a lot harder to work.
It has lower stretch than the dacron, which is why sailboat haliards
are often made up of stainless wire rope spliced to a working end of
double braided dacron.
* If stretchy rope is seen as an advantage...go for it. But the
working load rating on laid nylon rope is not as high as braided
dacron of the same diameter. My personal preference is low stretch
working line, of the largest diameter that's comfortable to handle.
1/2" is a minimum, in my experience, and it'll handle working loads
to 1500 lbs or so, with dynamic reserve. Well more than you need
for tower work.
* Bolts specified for racecar use are NOT necessarily stronger
than or appropriate for tower use. They MAY be; it depends on what
they were used for. You need to know the specs to know.
My personal recommendation is to go with Rohn galvanized hardware
everywhere. Zero doubts. Zero rust. Worth the price.