Nice Idea and thx for sharing. Could you try 3rd method with D grade stuff and ennchant it to +20 without broke? Then all will believe it is working on your server at least.
To others: some people are telling there are no enchant bugs,
others saying there are not 100% enchant exploit....
Re-check forum and you will see few 100% working enchant exploits - they were working. I knew 3-4 this type of exploits working on ALL servers so whats a deal with saying "there is no enchant exploit?"
You are right drinking potion A, B or C in correct order, enchanting in church or under water will never work but more sophisticated exploit were and will still work.