Ritual Spellcasting Variant

I thought I would write up my house rules regarding spell memorization. The standard rules of normal spellcasting in Basic/Expert D&D and Labyrinth Lord apply (verbal and 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 spell in their spellbooks 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 casting time is increased by another turn, followed by another saving throw. Repeat until saving throw is successful or spellcasting attempt is abandoned.
   
2. The casting must be uninterrupted.
   
3. Material components must be used.
   
4. The spellbook containing the spell must be available to consult during the casting.
   

Instead of burdening the system with specific material components for every spell, spellcasters may use a standard set-up for all spells such as a magic circle complete with candles and/or incense or a specially prepared potion used as a magical catalyst (and which cannot be made without access to a laboratory). Each vial of potion is good for one casting. The potion is used by drinking it, pouring it, or smashing its vial. Spellcasters may use either set-up at their convenience. The advantage of adding this method to the existing method is that spellcasters can continue to be useful even after they have used up their memorized spells (albeit at a considerable cost in time), it enables the creation of another type of spellcaster who is restricted to casting only unmemorized spells (witches, shamans, and other practioners of ritual magic), and it allows for a style of spellcasting more common in literature than the Vancian magic of the Dying Earth stories. I would use both methods in my game, but I can see using only the ritual method for campaigns meant to evoke a certain mood or flavor such as the fiction of Robert E. Howard or H.P. Lovecraft. [See also Ritual Spellcasting Variant 2.]

[Edit: Casting time revised 5 June 2014.]