I've been hacking together a personalized implementation of Ritual Path Magic for my setting/campaign. I've settled on the Effective-Shaping variant (introduced in Pyramid 3-66). However, I noticed one thing lacking compared to the standard energy-accumulation model: quirks. Since I want to keep magic a bit weird and unpredictable, I've come up with the following simple hack (drawing on the rules for Quick-and-Dirty Rituals and Charms):
Following a successful casting roll, make a second roll against the same Path skill, including the usual penalty of the ritual (including any bonus from Rote Technique), as well as any penalty for using multiple Path, but ignore any other modifiers. Success means the spell has no quirks! Otherwise, it has one quirk, plus another quirk for every two full points by which the roll failed. A critical failure converts the spell casting itself into a critical failure.
Example: an Adept character with a Path of Body skill of 18 attempts to cast Spontaneous Combustion (The Laws of Magic pg 8), which has a skill penalty of -11. He spends 1 hour casting the spell, offsetting the penalty to -5, for an effective skill of 13. He succeeds with an 11. But his second roll doesn’t include the bonus from taking extra time, leaving him with an effective skill of 7. He rolls a 12, failing by 5. The spell is successfully cast, but with 3 quirks.
For me, the fact that it increases the risk of casting a spell otherwise beyond the character's capabilities by just taking extra time is a feature; the RAW for Effect-Shaping casting time seems pretty generous to me otherwise, especially for Adepts.
It seems pretty solid to me, but I haven't had the opportunity to actually run RPM (in either form) yet, so feedback, especially from people with more practical experience with the system, will be accepted and appreciated.