You may have been watching too many films. I don't know that that scenario has played out in Australia at all. If it has, would love to hear details about which broker and when it occurred.
Find a broker which uses CHESS sponsorship rather than custodial ownership of shares. Simples! The bank account bit can be a bit tricky, but a trust account is usually setup, but cash is usually pooled as you say. There are ways to safe guard your cash if you have large amounts sitting in a cash account and you're worried your broker is the next Wolf... buy AAA with all your spare cash is one example.