I've been thinking that a boost pin like this would be ideal. Maximum adjustability but you would need to turn the cone first, then then do a second turning with different centers... It would be a universal pin that would allow complete adjustment from the most aggressive to least aggressive fuel to boost curve.
A boost pin like that would be nice but has 2 big flaws that I can see.
First - it's very difficult to machine. It would be most easily done one of 3 ways - very meticulously turned with a manual mill/lathe over the course of many hours, filed down by hand or run on done on a CNC mill ($$$)
Second - In order to have an extreme on one end for a well breathing engine, it would only work close to the minimum/maximum. If you set it to the middle but your extreme cut went deeper than half way on the pin, once you hit enough boost, the needle could go past the boost pin, get stuck out and jam the boost pin. Hello, black smoke and rev limiter!
The 1.6TD pin is like a moderate version of what you have there. Not a ton of range, but the same general idea. Unfortunately, they don't go too deep and are hard to find. I could either make a deep one or one with like 4 different settings, but nothing too aggressive.
I'm going to see if I can use a lathe at my old school for a few minutes and turn myself a boost pin and run it in my engine for a while... see how well it works.
For the block pressure tester, that would be pretty big. Talk to a metal supply shop and see if you can get some plate steel for cheap. 1/4" should be enough, then measure it out, cut it with an angle grinder or plasma cutter if possible and drill holes for the head bolts with a drill press. That's exactly how I'd make it.
My biggest hurdle might be finding somewhere to keep/use it. I've got a few friends with shops that would have the space, hopefully one of them would have use for it and let me store it in their shop