We Are Sorry to Interrupt This Spell

I have come to the conclusion that spell interruption makes no sense in the context of Vancian spellcasting. In the Dying Earth stories by Jack Vance, it may take hours to memorize a few spells, but once a spell is in the magician's mind, coiled like a spring, all he or she needs to do is utter a few syllables to unleash it. I imagine the effect being as immediate as the killing words in Dune. Ritual spellcasting is another matter. Spells cast ritually are not memorized (at least, not in the same manner), but the casting time is greatly extended, affording ample opportunity for interruption. Coupled with an additional cost (such as possible hit point loss or temporary attribute reduction), ritual spellcasting becomes a viable method of extending the spellcaster's usefulness without resorting to power inflation (in theory, I should add, as I am currently playtesting it with Swords & Wizardry White Box). Dispensing with the idea of spell interruption for memorized spells helps me in two other ways. First, since I am no longer using the complicated combat round sequence of post-OD&D, I no longer have to worry about requiring spellcasters to commit to a spell before initiative is rolled — they are as free to cast or not cast as anyone else who is free to use or not use a weapon. Why does this matter to me? It matters because the game flows better, and when the game flows better, my players and I enjoy it more. Second, it preserves the value of memorized spells in contrast to ritually cast spells. And since I'm using Brendan's Simplified Spell Progression (i.e. reduced spell capacity), it's all the more important that the memorized spells become the reliable ones.

(I probably ought to note here that I am not observing the variable casting times of certain editions of Dungeons & Dragons. In my campaigns, memorized spells are cast instantaneously, whereas ritually cast spells have a uniform casting time of one turn [ten minutes].)

Here, then, are my latest revised rules for ritual spellcasting...

Ritual Spellcasting Variant 3

The standard rules of normal spellcasting apply (verbal and/or somatic components only; casting time of 1 round; memorization of all spells in 1 hour after 8 hours of sleep), but spellcasters may also cast any currently unmemorized (or unprayed for) spell that they are qualified to cast (i.e. are of a high enough level to cast) with the following restrictions:

1. Casting time is increased to 1 turn, after which the spellcaster makes a saving throw vs. magic. If failed, the caster loses 1 point of strength per level of the spell. Strength lost in this manner is fully recovered after 8 hours of sleep.
   
2. The casting must be uninterrupted. If it is interrupted, the spell is disrupted, but the caster must still make a saving throw or lose strength as described above.
   
3. Material components must be used. Magic-users may use either a magic circle with candles or incense, or an alchemical catalyst to be imbibed, poured, or otherwise destroyed. Clerics may use items appropriate to their religion and culture such as censors, holy water sprinklers, bells, chimes, gongs, prayer wheels, candles, bonfires, etc.
   
4. For magic-users, the book containing the spell must be available to consult during the casting. For clerics, a holy symbol, holy book, or sacred object must be present.