Creo vs Rego Crafting

I'm currently debating the merits of "casting a spell a bunch of times, hoping to do it better is, by definition, a ritual/ceremonial casting."

Which is why I like the idea of having the Ceremonial Casting automatically integrated into all forms of casting - at its heart, you're really just doing the same thing over and over again, hoping for a better result. The AL+PH represents your ability to link all those attempts together in a cohesive whole.

Of course, there are lots of spells that you would cast multiple times in a row normally - such as Pillum of Flame, or something. In that case, I would argue that enough has mystically changed since the last time you cast it (ie, your target moved, you moved, someone has tried to kill you, etc.) that the mystic nature of the scenario has been reset, and thus you can (potentially) roll better.

But if nothing has meaningfully changed? Well, then you'll just have to wait for the default hermetic change: sunrise or sunset. (Which is not to say you can't cast again - you just won't do any BETTER - in fact, you may do worse.)

Of course, that's just a bit of in-game justification for keeping players from doing the perfectly rational meta-game activity, due to a quirk in the game mechanics.

There is a really trivial way to adjust difficulties and incorporate skill with the actual craft if you want to do that. Just adjust one or both of the -3 and the bonuses from having associated knowledge (HoH:S - Jerbiton chapter), probably mostly the latter but if those bonuses get high enough you might change the -3 to a bigger penalty. For example, you could just add the associated Craft Ability's score of let's say 7 instead of capping it at 3. Then the magus who knows a lot about the actual craft will be much better at it than the magus who does not.