The problem with admitting all these small economically countries into BRICS is that the organisation starts to lose it's purpose. What's the criteria for not letting a country in? Can any country that aligns politically or economically with China get to join?it's been rumored for a while that both India & Brazil are cautious about expansion and you can see why.
Anyone joining BRICS would be seen with motively partly to get closer to China, so BRICS expansion helps China. Russia is isolated by west, so expansion of BRICS also helps its power. South Africa has very little power, so expanding BRICS helps its position as a founding member.
On the other hand, both India & Brazil are powers in their own right, so expanding BRICS diminishes their influence within BRICS.
As such, they are likely to only favor countries that they are friendly with like Argentina for example. We will see, if I had my choice, I'd rank desirability as:
Indonesia
Saudi
Argentina
Iran
UAE
Nigeria
A lot of places with resources, population. We will see. One that represent global south would be one that China can grow its strength while giving it some cover
BRICS ought to serve as a counterpart to the G7. When founded, G7 was the largest 7 aligned economies in the world. Things have changed a little since it was founded, but the principle is still there.
It should be limited to $1 trillion+ economies only. South Africa was only really admitted for political reasons, but it would be rude to kick them out. Presently I think only Indonesia and Mexico are the countries that need to be admitted. A seat to the GCC would be a good idea, since they virtually operate as a country.
But the likes of Argentina, Turkey or Nigeria, no. They can join the SCO or the BRI.