The quickswitch works more or less like any other cocker "3-way" valve. The difference lays in PPS's model's modular design. The quickswitch's cup insert things make it possible to set a nice and short throw, easy to maintain and one of the most all around user friendly and reliable designs out there. Per my last pm, I think using the quickswitch cups to integrate a whatever-way into your auto-nelson design it the best possible idea, simply because apart from all it's positive qualities it would be much simpler to install the quickswitch cups (not the whole three-way, just the cups and the seal kit) than it would be to adapt another whatever-way or even set up a MSV or a couple submarine valves.
Also ask have blue if he knows about any pistons/rams with one input and a return spring with enough tension to move the cocked bolt/hammer assembly into the close position. Other than going the quickswitch cup/seal kit route, I think using a submarine valve with a piston with a strong enough return spring is the ideal route.
Something I noticed, or rather didn't notice, in your CAD pics in your first post to the thread is a lack of anti-kink device (what in cci lingo is referred to as an TPC - tuned port compensator). Even with a powertube with a beefy OD and a hammer and/or bolt with the same, you absolutely need some sort of anti-kink system in place. Especially considering it's going to be a semi-auto pneumatic gun. Of course you would probably make the powertube longer and set it up to also function as an anti-kink system, especially considering you're auto-nelson looks like it will be a bore drop based nelson design. If not doing that though, make sure to add something like a TPC or the Lapco Grey Ghost's velocity adjuster that also functions as an anti-kink mechanism. Oh yea, and on that note, as opposed to using a longer powertube as an anti-kink device, you really should think about installing something like the Phantom's TPC or the Grey Ghost's velocity adjuster/anti-kink mechanism. Why? Because it would be the easiest way of adjusting velocity! Well, assuming you don't like to have to take apart the gun and change springs or use shims to get your velocity set right every time you go out for a game or two. If you're going to run an inline reg, prior to using an LPR to feed the whatever-way, you can use that instead to adjust velocity. But other than using an inline reg, afaik a TPC/velocity adjuster/anti-kind mechanism is your only real options when it comes to being able to externally adjust your gun's velocity.