I'm not sure why someone would refuse to use gauge on Intervention.

I personally feel that actions should be designed to be versatile rather than niche. A simple change is all that is needed to do this for Clemency. All that you need is a proc that can occur a maximum of once per 60-120 seconds that makes your next cast of Clemency free and instant. Under normal circumstances, this is just your standard Equilibrium/Aurora equivalent that you can weave in as an oGCD. If you need more healing output than that in a pinch, you still have the option of hard casting it to keep yourself and your team alive. We haven't taken anything away, we've just made it more versatile. There may need to be some balance adjustments in terms of MP cost and so on to offset this, but the concept is what needs to be looked at.

Cover is a fairly iconic PLD action, dating back to FF4. I think that its historical interactions with things like Earthshaker and transferring debuffs were unintentional. Part of the problem currently is that it occupies a similar function to Intervention while having a gauge cost attached. It probably makes more sense for Cover to upgrade into Intervention and bring along that flavor effect rather than trying to compete with it for resources. What you could do is introduce Cover at Lv. 45 as an ability that only transfers damage across that would otherwise kill your target, and then upgrade the effect at Lv. 62 to Intervention. That way it retains the flavor and allows you to clutch rescue a teammate, but doesn't force you to take that extra damage unless its absolutely life threatening.

I'm actually not sure why they feel compelled to keep in both Passage and Veil in the first place. They probably could get rid of the heal requirement on Veil. Passage doesn't really need to be changed. I think if you give players a chance to practice and learn how to target cones, they will. Not everything needs to be converted to a circle.