I think there's a range where the preload can be useful, it's just a very small range, to really effect the proper change, a re-valve is necessary. The stack should be tuned correctly to start, then play with preload. You could though just build in as many circuits as you want, the valving would get more and more complex, but you could have multiple mid-valves and adjustments, blah blah, it would get exponentially complex and past the point of benefit quickly most likely.Shim preload adjusters are for HSC. The needle bleed adjusters are for LSC. They're both as real as steel, but do different things.
I find the bleed adjusters to be more useful for myself. I also think most riders are best off with only external low speed damping adjustments, with high speed/shim preload adjustments as an internal adjust/revalve feature.
Magnets.