Can Sanji free himself to that bracelet using armament haki? or is it really indestructible that there's no other way but to use the Key?.
Rayleigh was able to remove Camie's explosive collar back in the auction house. Luffy probably learned how to do that too during his training with him.
The only way he could've learnt how to do it was if he had practiced it on someone, so I don't think he knows how. Plus, destroying it would be the so called "easier way" so he wouldn't choose it
What do you think?