GURPS Martial Arts pg 215 expands
GURPS Thaumatology: Sorcery pg 28:
- immune to crushing damage, loses no more than 1 HP from any piercing or impaling damage, and takes full injury from all other attacks
- On how it is used in combat , 
- On getting a Defense Bonus , 
- On throwing a cloak to entangle an opponent 
- you can defend with the same thing you used to attack (e.g., whip a cloak and then block with it
Douglas Cole quoteEdit
So: switches, not mandatory "yeah, if you built your character around this, you can't use the new rules without nerfing him" actions.
Well, except for Cloak and Whip. I was given permission to tone those down a priori.