It is not recommended to use brains but if my practice is diversifying my coins to different wallets, at least I will try to use my brain and memory to remember wallet mnemonic seed of a biggest wallet.
For me I don't think a brain wallet is a good solution to immigrants saving their passphrase, it is dangerous. If I'm an immigrant and I know I have a limited stay over there either because of being deported, I will look for means to project my wallet passphrase and for now what is coming to my mind is saving it in my email and then safeguard my email password and using strong security like 2FA so that before you break into my email, it will be a difficult task.
What about having a USB with no attachment to the Internet with the said keys? - After all, why have it somewhere where somebody would be able (potentially) to get it?
The chances would be smaller with a flash drive or something like that rather than going for the Email, imo..