Good post. This might be a slight derail, but: I wonder if part of the problem with getting people to accept this is the use of the value-laden word "trust". Many people immediately react to this concept with horror: they don't "trust" the government in the same way they trust their spouse or their parents. I wonder if economists would do better to replace "trust" with "future expectations" or something like that. [Edit: when presenting to mainstream audiences.]
Predictability is probably a better word; uncertainty is enemy of business planning, far more so than unfairness or corruption or incompetence. Business (writ large) is just fine with incompetence or corruption, as long as it can plan around it.
The talk about "trust" is also problematic from an empirical point of view. You see plenty of people who loudly proclaim that they don't trust the government / the Fed / any official institutions, yet you seem them using the currency provided by those institutions. Clearly, trust is not what gives the currency value.
Granted, those people may not have their savings in assets denominated in that currency (if they have any savings at all), but - in line with what you write - investment decisions shouldn't (and rarely do) have anything to do with "trust". Consider that security-thinking folks more or less define a "trusted person" as "somebody who can undermine your security".
I hear that used sometimes and I think it's better than trust, but it still holds some connotations that seem undesirable for the purpose: right now, a significant number of people in the USA seem to dogmatically believe that the government "can never be trusted"; these same people, if asked how much credibility the US government has, would say "none"! Etc... basically, there are lots of people that see "government" as pure evil and they make their decisions and form their beliefs around that. IMO it'd be really nice to change that, of course; but as long as people have extremely emotional responses like that, it might also be worth looking for ways that word choices can be made in order to make communication more accurate.
Frankly I don't see this as a problem with accuracy of terminology. Both trust and credibility are perfectly adequate and sufficient terms. The fact that money has any stability at all is testament to the fact that a majority of the people who use it do 'trust' the 'credibility' of the government to manage it, whether a bunch of wingnuts think they ought to, or like the terminology used to describe it, or not.
I personally have no issue with the word trust in this context. My concern is with the many people who vote and who aren't educated about what its specific meaning is in this context and react to the word emotionally. In the case that the participants in the conversation are trained in economics, "trust" seems exactly the right word to use.