Can/does bleaching with Kaleidocolors Blue (or other colored bleach) prevent the need for a toner?

Very rarely. The odd person lightens to a nice color without a toner. Lets say 1 in 100 heads. Those people are usually blond to begin with. The blue/purple is there to help with brassy tones but it really only helps. It cannot prevent 100% unless you are one of the lucky few who lighten to a beautiful tone naturally.