But how many people are actually going to abuse/power game like that?
I want to believe that people won't abuse a mechanical advantage opportunity like this, but it unfortunately is just not the way things will pan out. If a powergaming opportunity exists, there will sadly always be an ever-growing number of people that will use it to its fullest extent, using the argument of "the rules totally allow me to do this" as validation. Even if it just starts as one person, others will start to see them doing it and get inspired to do it themselves. Even if there are people that see it as cheesy and don't do it themselves, they'll start to feel/get left behind (metaphorically, and possibly literally) when less-concerned players around them start using that strategy, making them feel less valuable on the field because they're reluctant to give in to a powergaming opportunity, until they eventually do give in and join the popular movement in order to feel on-par with everyone else. From there, it will just become The Way Things Are Done™ all over the place. Sigh. Oh well.
That said, I do agree that there's a lot of potential for this to get abused very quickly. A skill that lets you use some other daily skill without expending it is a recipe for people to use their highest-impact skills over and over, completely allowing people to bypass the prerequisite structures designed to limit the amount a person can typically use that high-impact skill. I appreciate the general concept that Riposting Strike is going for, but in its current incarnation, I think it's going to get out of hand.