I'd love to see something similar for encrypting a 12/24 word seed. Even better if the result is just represented as a seed again: to restore, enter the encrypted seed, the password and wait a few seconds (yes, seconds!) to decrypt it. I'd feel much safer than just storing the unencrypted seed words in plain text.
I think a person can implement exactly that process in a very trivial way. For example, say you are using the bip39 english wordlist. Say your mnemonic is 24 words long. Then you need to generate 24 random integers between 1 and 2048. Those 24 integers are your passphrase. They will serve as "offsets" when they get added to the indexes of the words in your unencrypted seedphrase. The addition is modulo 2048. Done. Now you have two things to keep track of instead of one but I guess that's the price you pay for having an encrypted seedphrase. As long as someone doesn't get ahold of both of those things, they can't do anything.