I do wonder though if Powerplay has proven that this way of thinking (trusting players to do the right thing) just shows a lot of players are idiots or don't care, nullifying any positives from the design. Being honest there is a hard-core of players who do indeed care and do the right thing, but are constantly fighting either idiots (5C) or those who are ambivalent which is more like babysitting than being fun. For me its telling that much of PPs updates / planned / might happen / dreams etc are more to do with trying to rationalise / temper poor decisions rather than add anything extra that might attract more players.I fear the day that over-fortifying a system stops (or slows) giving merits. Those people fortifying to thousands of % over the triggers are simply looking for the fastest, laziest way to make their 50,000,000 salary and go. If fortification supplies stop being the easiest way, then it'll be preparation merits, or if preparations stop being easy it'll be fortifying more systems than is good for a power and driving CC up too high.
If mechanics are added which limit player actions based on what's "bad" or "good" then the Powers lose a lot of freedom of action. Powers prepare "bad" loss-making expansions in hostile territory all the time. They also prepare "bad" systems in the interests of player groups, or to close holes that other powers could choose to weaponize against them.
With freedom of choice comes freedom to fail. It's important to give players a chance to make bad strategies, because then the good ones may shine through.
For Powerplay to be self sustaining and 5C proof I do wonder if it has to be more like the BGS (i.e pseudo random expansion / contraction) that decentralizes a lot of the choices (in essence everything is a local branch) and decouples negative outcomes from expansions (which 5C use to good effect, just as weaponised expansions are). It would diminish the strategic aspect as we know it, but might make for a more granular territorial game overall.