The big 4 in Australia are referred to as the 4 pillars for a...

The big 4 in Australia are referred to as the 4 pillars for a reason.
If one of the Pillars does one day fall we are all going with them.
The policy structure is that none of the four can merge with an other one of the 4.
This ensures Australia will always have a strong banking system competing with each other to give Australians the best possible outcome in banking.
Our banks are not perfect.
Some of our bankers over the years have behaved in a dishonourable manner.
However , I have chosen to invest in Australian Banks because I believe them to be as good or better than other banks across the globe. I am sorry for you if indeed you chose to invest in smaller banks that went down the spout.
My point is , In my most humble opinion I believe that to build wealth into a Share Portfolio in this country you must include at least one of the Big Four. Like them or not. !!!!