I might be. Although I am giving this thread some background thought.
Certain martial fighting styles have a discipline of "every punch is a block, and every block is a punch", while others just "block" and do nothing with the result.
Wing Chun and "Sticky Hands" would be something to consider, relating the the first. Other styles also turn a block into throw or joint lock, such as Eagle Claw or Aikido.
The first thing to consider would be whether a practitioner knowingly acts with the intent of follow-through action or whether this happens by chance.
It would complicate a system if it took into account the degree of "follow through" that a practitioner had trained in and developed though experience. And which player would deliberately choose a "weaker" skill that represents a fighting style that does not encourage riposte? I guess a riposte capable skill would be more expensive (although once understood, the concept is easy, and becomes an attitude), or a secondary complementary skill could be used, such as the "martial-art" skill.
I like how Steve's SPQR uses "levels of success" with one of the options being riposte. Such that a really good parry leaves the opponent open for a counter action. Maybe a "special" result for a parry could allow the chance to riposte, but then a skilled practitioner aims for all blocks to follow-through, which means that it should occur more often than "special" when a counter-action is intended.
If (in a fight) I have the opportunity to shield-jab (with edge or corner) someone in the face, I would take it. Part of the skill of "fighting" or combat strategy is making those opportunities.
Just some food for thought.