"I also would look at tower construction or design as the problem."
How much do you want to pay? Those towers are often suspension systems. Ie the wires are part of the support system to hold the tower up. So if you lose the wires in a high wind or a tower is damaged and fails you are at risk of losing the towers in that area because they lose a large part of their structural support
There are often heavily engineered towers every so often to limit the cascading collapse that will happen if something does happen.
You can engineer things to withstand almost anything but at what cost and is it feasible to engineer HV transmission towers in SA to withstand a high cat2 storm when it happens so infrequently.
Also cascading power network failures are not uncommon. Lets not get carried away here.