There is less critical ambiguity in the triad weapons. HS weapons introduce ambiguity in the above calculus. So with former, the global mafia could (safely) play proxy war in far flung location. Now, they can't do so, safely. All members of the global mafia cartel are concerned, since proxy wars are very good for [(settling)] business.

There's no ambiguity only because nobody has bothered to mount conventional weapons on ICBMs. There's nothing preventing that, and indeed the US has seriously considered it as a way to implement Prompt Global Strike. Those plans have been held back by the fear that launching such a weapon could be mistaken for a nuclear launch, of course.

Is the problem with hypersonic weapons just that it looks like the players won't make that same choice?

Based on the arguments in this thread -- I don't see the difference with respect to m.a.d. either.

HS launch could carry conventional or nuclear threat, it's not possible to know which after detection of launch. For mad, we must always treat these launches as nuclear -- and therefore in the end, no one uses these weapons (unless they are intending to launch global nuclear war)...?

> All members of the global mafia cartel are concerned

Who are these members?

A lot of the apparent ambiguity could be resolved by looking at the number of launches and their trajectories:

A) there are simultaneous launches against many different targets. Conventional or not, the enemy is trying to remove your ability to retaliate. The implication is clear.

B) Only a small number of weapons have been fired off at one or just a few targets. Even if the weapons inflict heavy casualties, your ability to retaliate remains intact.

There's another option as well: have enough redundancy to have substantial forces survive even a massive first strike, absorb it, and then retaliate at leisure. This seems to be the US's approach:

https://www.armscontrol.org/act/1997_11-12/pdd

I imagine other countries with smaller arsenals may not have that option. Even your B may not necessarily be an option, if their command structure relies on centralized control and would be vulnerable to a decapitation strike.