Not sure I follow. Only upside for whom? My point is that the USD for all its warts, is a better, more stable currency to use for trade between BRICS countries than any of the currencies participating in BRICS countries themselves.

Except that they (the Fed) manage the supply, and ‘printing new dollars’ costs whatever it costs for a few banks to change a few bits on a few hard drives.

I see only upside…?

Think of the stonk loads of additional currency demand that exists independently of and over and above trade exchange requirements. A Dutch disease, of sorts.