Right, that is actually why I am trying to focus more on the error-correction aspect of this. Using a secure hash function for checksum calculation (as in the bip39 spec) helps determine that there is an error but it does not identify where the error is nor help correct it.

Reed-Solomon error correcting codes are more what I am seeking, but it is non-trivial to make those work for permutations.

Anyway, there seems to be less interest/activity in this bounty thread than I was anticipating, so I went ahead and awarded the bounty to you!