from the outside it looks like an unregulated, impossibly opaque fractional reserve system.
Its pegged to the dollar, or what ever. But none of them are resilient against a run, well, not and be profitable.
There are still some risks (company will get hacked, executives will go rogue, banks won't be prepared for a major run) but these are fundamentally the sort of risks that the US banking industry has some experience with. These risks have nothing to do with what's going on at Tether: they don't seem to be regulated at all.
A: "...an unregulated, impossibly opaque fractional reserve system."
Answering your own questions, well done. :)
In either case offering a price in USDC for example would meet your needs. Your customers can pay in crypto but what you get is essentially the same as dollars (excluding transaction fees), so goods can be priced the same in crypto and cash and you're not exposed to crypto volatility on your holdings for the most part.
So if you have a use case for businesses to price things in a stablecoin, then it follows that there are use cases for people to get stablecoin to use and therefore usecases for creating stablecoins, exchanging them for other crypto etc.
The problem is not one of theoretical possibility, the problem is one of perverse incentives. Tether's operators have no reason not to go to Vegas and put all that money on a coin flip. Heads they win, tails their 'clients' lose. They'd be idiots to not do something like that.