I always wanted to shoot a line over a limb of a bigleaf maple out on the Hoh and explore the moss gardens with their unique epiphytes and orchids, but was always afraid the tree would shed my limb while I was up there. I guess big doug firs are a lot more stable, but you've still got more guts than I do. 
I remember seeing a big inflatable "wheel' that had been set in place in a S. American rain forest to enable researchers to scramble about researching, but I wonder if a cable could be tensioned amongst the big trees that could have trollies running on them that could raise and lower climbers without putting any stress on the trees, or at least provide backup suspension in case of a failure to suspend. Nah, I'd still be chicken. Too many things that could go wrong. Me fall down, go splat.