If the stablecoin issuers have their assets backed by dollars (which I'm not convinced is even necessary, but I also think there needs to be some kind of constraint on their issuance), they could conceivably serve as high-level market makers of last resort, if you will. Or lenders of last resort, but I'm not sure how it would work, or why an entity like Nexo would take out a loan when it can just sell assets it doesn't need in the short term, for dollars it does need in the short term.
But doing so would require that the larger market maker has a big ass pool of dollars to provide liquidity with,