It seems like there are two pools of rituals; ones with utility that can be measured on a per day basis, and those whose utility has more of a narrative focus during down time.
Casting knock from sunrise to sunset on a non-adventuring day doesn't have any real impact on the story, any more than having a high lockpick. It's only impact is during an adventuring day; thus, it should be able to use adventuring day resources.
Other things have a deeper impact, like hand of fate; given a week of down time an unlimited (or even daily resource) ritual casting and some of the scry effects can be pretty abusive. Its results are more long term, and that knowledge starts to become tangible, and it has a value.
The catch is, the adventuring day ones need to be done in a way that doesn't overrule a trained class.
Healing Surges could work for this; it's a significant investment.
Burning a daily would also work.
I think I like Action Points best of all, because you can't just burn through them at once.
Also, for something that removes a skill, letting the ritual just act as a conduit to use Arcana, Nature, or Religion in place of that skill for an encounter/round might help keep the other PCs engaged.
There is another option, something I have been messing around with in my notes called "Mystic Lore." It is, essentially, of a kind with Master Training or Divine Boones. A non-item ... Item, that essentially grants a daily or encounter power. Daily uses of this power would use the "Daily Magic Item Power" resource (needs a better name), preventing abuse in a similar way to the Action Point idea.
So, knock could become a daily power that you spend gold to learn, that lets you use Arcana in place to Thievery 1/day or 1/encounter.