I believe that Qantas do not count RAA time.
Some would consider ag work a career and not just something you try out on the way to the airlines so in order for someone to "give you a go," on ag flying, it might take an adjustment to your attitude towards using it as a stepping stone.
Another thing, your timeline may need reviewing. 10-20 years in airline has you starting at 45-50 years plus which would be moderately difficult to achieve. You'd want to be heading there much sooner if possible.