As best I can tell, this new foreign minister is local Swamp filth inserted to prevent the new president from draining it too very much.
I would not celebrate this too readily. The overall goal of this new guy is to pipe gas to Latin America as a whole. The Vaca Muerta in western Argentina has shale gas (and oil) and the pipelines are underway. This will erase LNG customers from US export desires.
The intriguing thing unfolding is when that gas flows, odds are not bad the IMF will be told to GTFO and accept an Argentine default. When you have gas, oil and fuel, you face no consequences if you default.
So, overall, do not imagine co-opting this new guy into US favorable configuration. I would expect the Swamp minister to be booted and a reversal of BRICS decision far more likely than repaying the IMF.
Javier Milei ran against BRICS.