I haven't really gotten beyond trying out the game and was thinking about this optional rule. My concerns are that it may unbalance the system somewhat. Using techniques straight from the book will not change that much, but techniques designed with this rule in mind, e.g. using only the primary characteristinc to determine the amount of Ki needed, will be unbalanced.
My question is, how do you handle this? Do you allow it to happen, do you force players to create techniques that are just plain badly designed under the rules-set, do you limit them to ready made techniques, or what?