They could start by making it illegal to use money from a home loan for anything other than improvements to the property. I regularly get letters from banks trying to get me to pull money out of my home loan and spend it on luxuries.
Every week I get letters from various institutions trying to get me to borrow at high interest rates. This is not new, it has been like this for a long time. Mboweni is at least aware that the banks are out of control, pushing credit constantly. It might take creative measures to discourage them.
I don't think the level of borrowing is the real problem. Capitalist society runs on credit. The problems appears to be that supply isn't keeping up with demand, leading to increases in prices. South Africa needs to increase its capacity so it can keep up with consumer demand. If we can boost supply and maintain demand the economy will benefit.