I've always wanted to make a patcher that has redundancy built in, so you could use it like

file thats mostly like arbitrary file A + patch file = arbitrary file B

No more "rom hack doesn't work because you have the wrong region dump" or "can't send this because copyright" or "can't make a patch since files are watermarked"

The idea is to essentially encode how to create file B from the content of file A in a position independent way, for example "grab N bytes after pattern X", and give it plenty of alternative operations it can take if an operation isn't possible, as checked by CRC blocks