In addition, equal share system won't work. The five nations in the BRICS have different financial strength with China way more stronger.
If you want to have equal shares, you have to not only contribute equally but also contribute additional funds later equally.
It will be hard to keep that going all the time.
Not a single major financial organization in the world works that way.
Even political organizations do not work that way as well.
Just like a firm's IPO dictating each shareholder buys the same amount, and cannot buy more or less so as to achieve equal rights among all shareholders.
Have you seen any public company doing so???
Maybe communist time.
An equal-share based BRICS bank won't last long and won't work well either.