An advantage and disadvantage of Ritual Path Magic is that you can do practically anything, including really game-breaking Greater Effects, as long as you can gather enough energy for it. Certainly, the GM can just go 'Nope!' but this can get pretty frustrating, and sometimes SoD-breaking, if you haven't made a rule in advance. You
could forbid Greater Effects entirely, but that would be a different thread. Thus, I've thought of a few ways to limit just the Greater Effects (though it's possible I may have read one or two of these elsewhere, and one I know I did).
Firstly, let's say that Ritual Adept only applies to Lesser Effects, and you need another, more expensive advantage for Greater Effects. I would go with Greater Ritual Adept having a cost of 400 points, and contain Ritual Adept, so you don't need to take both. This allows the Final Boss of the campaigne to throw out Greater Rituals on the fly, but still limits the PCs and most NPCs, save in especially high-powered games. Tailor the cost to your setting, of course.
Next, suppose that Greater Rituals are more specific - you don't just need to take enough time to gather the right amount of energy, you need to start (or finish) the ritual at midnight, perhaps under a full moon on the Winter Solstice. You don't just need a Ritual Space, you need to perform it in the Temple of Iupiter Optimvs Maximvs in Rome. You don't just need an apple, you need an Apple of the Hesperides, or an olive branch from the highest (not tallest) olive tree on Mount Parnassus. The Greater a ritual is, the more restrictive each component is, in other words. This not only limits Greater Rituals, it's nicely genre-appropriate for a lot of stories your game might be inspired by.
This one I know I've seen, and fortunately, I know who said it: On Ravens N' Pennies, Christopher R. Rice did an article called
Beginner's Ritual Path Magic. Have a look, but to summarise it, if you've never cast a particular spell before, or haven't cast it all that often, you get a Familiarity Penalty for it, until you've practiced it enough. This does restrict Lesser Rituals as written, but it's more limiting for Greater Rituals, especially when combined with the above. Depending on the GM, a grimoire might offset the penalty by more than its bonus, to the point that even a +0 grimoire might be helpful (I know I've seen +0 grimoires suggested for RPM before, but I'm not sure where).
So, does this look interesting?
What effect do you think these rules would have on a setting like Monster Hunters, and what on a setting like Banestorm, where this alternate RPM would replace another magic system?