2. Ships or personnel that can just keep on stacking stress. I cannot see how massive piles of stress is logical. If one stress is equal to a ship not being able to focus, TL, barrel-roll, etc. Two should double that hindrance, like make it unable to shoot or defend during an attack phase. Heck, three times the stress that keeps a ship from acting should make it unable to move at all. Maybe four times the stress should make the life support systems start to fail. See the logic? The effects should be doubled with the first addition of stress and then tripled, and so-on and so-on....not simply put in a pile.
I see your point. Part of the problem, though, is agreeing on what stress actually represents. It was originally pilot stress, as indicated by the "check pilot stress" step. The idea is that you are distracted by something such that you can't focus or take other actions that require skill. In the core set days, doing a Koiogran turn was stressful to the pilot, so the pilot couldn't focus after (basically during) the Koiogran turn because they were trying to pull off this very difficult maneuver.
But since then, we have things like Flechette Cannon and R3-A2. Just what exactly are these upgrades doing to cause stress to pilots? Wouldn't a 4-dice heavy laser cannon cause you just as much stress, if not more? So what we see is that stress has become increasingly abstracted. It is a game mechanic now with echoes of theme. Stress is now used as a way to balance cards instead of or in addition to using squad points. Part of this is the nature of game expansions. As you expand a game, you'd like to explore all the design space offered by the core rules before you start introducing brand new mechanics. The stress mechanic was ripe for exploration, leading us to the situation we are at now, where stress is a much more abstract game mechanic than it was back in wave I.