If international settlement agreements could be reached among BRICS countries, the BRICS currencies would only be useful in trade with the originating nation. In other words, while South Africa and India may agree to settle trade in rupees,
it is unlikely that other nations would accept rupees in trade with South Africa. Furthermore, several of the BRICS countries carry a large amount of foreign debt, which must be serviced in U.S. dollars, not rupees.
Consequently, South Africa would sit on a pile of rupees that would be useless for any purpose other than trade with India. To make matters worse, while holding the rupees in reserve, South Africa would be exposing itself to currency valuation risk.
International traders use the U.S. SWIFT system to process cross-border payments because it is safe, fast, and accurate. Most importantly, it is convenient as it connects with major banks in
over 100 nations.
China and Russia have attempted to build SWIFT alternatives, but neither system connects with banks in Western nations.