"Oh no, both are invalid!"
"Maybe it was the 7th and 9th word!? No, empty wallet as well"
"Yeah, now I do remember! I decided to change one word with the preceding one! Or was it changing the second word with a word 2 down in the list? Was it 2 up?
TL,DR: Don't be your worst enemy. KISS principle is the way.
Bitcoin Q&A: Why is Seed Splitting a Bad Idea?
Splitting seed words or trying to encode it in creative ways will make recovery process more complicated and more risky to fail. Because after one or two additional encoding chains in the process, if you need to recover your wallet from encoded backups, you will have to decrypt it.
Many risks will cause the decrypting process fails that will make the wallet recovery process becomes a nightmare and failure is unavoidable.