Disclaimer: I am neither knowledgeable enough about economics nor the Mercosur situation.
That said, I have an honest question for whoever may want to chip in: why would a single currency be bad or good in the case of Mercosur?
On one hand, I could see a single currency simplify trade over there and be perhaps less volatile than all Latin American currencies, on the other I see very different economies and so the opposite might happen (aka, they’re so volatile that the single currency would fluctuate in weird ways due to country X or Y having different scandals or issues)
I suppose my question is if asymptotically it may help stabilize all countries a bit or it would just not work amid such a diverse pool