Hal wrote about Bitcoin banks before Satoshi had invented merged mining. It was the obviously simple scaling solution, but they continued to develop and build.
Bitcoin banks will suffer the same fate as gold-backed banks. The solution is multiple "medium-size" blockchains.
So instead of 10GB blocks on L1, we have ten 1GB sidechains + 1MB L1, secured by Bitcoin miners and cheap enough for businesses to run full archival nodes.
The rest of us can use SPV wallets (and still run a full L1 node), which are massively better than custodians.
