With the OSR Project, I ran into a snag trying to develop a magic building system. I wanted something that could re-create the spell list from B/X (or BECMI) without being overly complicated.
One idea was to use the OpenD6 system. The downside of it was that this seemed to lessen the number of spells. In other words, fireball and lightning bolt become essentially the same spell.
Then, I remembered some ideas I had for Shayakand based on Anaxagorian philosophy. For the system, we could use Seeds and Essences. Seeds are what you might call elements in either the modern or classical sense. This would include air, fire, water, etc. You can even throw in oriental elements like wood and metal. Get alchemical and add in mercury and sulphur and aqua regia. Get modern and include gold, silver, helium, sodium, etc. To make it more like Anaxagorian, though, you'd have to include what we in the modern world call compounds (including alloys). With this we have salt, baking powder, diamond, pewter, concrete, etc. Seeds could even include metaphysical concepts like thought and newtonian concepts like force, gravity, and the like.
Essences are easier to describe. They are the fundamental qualities that make a thing distinct from every other thing. For example, human-ness would be an essence. Orcish is another one, elven would be a third example. It doesn't necessarily apply to sentient creatures (all lumped under kith), it could be specific types of animals, plants or protozoan. In a world with magic, you have to have unlife, but you could have something as weird as chair-ness. (The essential qualities of a chair that make it a chair and not something else.)
Anyway, seeds and essences would make the NOUN part of the magic system.
For the verb, I'll like to stick with common categories for now. This would be things like Protect, Curse, Charm, Create, Summon, Change, Heal, Imbue, Move, and something for Illusion spells.
So the basis of creating a simple spell is to link a verb to a noun. Create Gold, Move Thing, Charm Dragon, Curse Weeds, Summon Fire, etc. Imbue and Change are similar, but the difference is this: Change transforms one object into another. Change Frog would transform the target of a spell into a frog. Imbue Frog would impart froglike characteristics to the target. This could be anything from a long tongue to the ability to breath through the skin, to an ability to sit in water for long periods of time without becoming dehydrated.
After that, we'd need a point system of some kind to measure the effects of these spells. For example, a simple spell could pertain to a 1hd creature, 1 molar of a substance, 1d6 damage, or +1 effect. These spells would cost no points and could be treated like cantrips.
To enhance the effect, though, would require spending points to increase the area of effect, the range of the spell, increase damage, increase number of targets or modify the casting time. Not sure about the specifics of this one yet, but I'd hope that a point system would only be used to generate leveled spells. In other words, a 2 point spell could be first level, a 4 point spell could be second level and so on.
The effect of this system is that spells and magic items are incredibly specific. Here's what I mean. You can have a spell that temporarily protects you from attacks by a type of creature. Even if you broaden it out and say Protect Animal, you can be harmed by plants. If you say Protect Living Creature, you can be attacked by undead and constructs. There is no "protect everything" spell. "Everything" is not a seed or an essence.
Thinking about the spells needed to create magic weapons, there is not a generic spell to grant +2 against everything. So magic armor could be +2 against kith (all sentient creatures) because it was created for a soldier to wear in a war. Maybe a +3 against dragons for a local hero out to rid the area of a pesky dragon. In other words, it give the magic item a story because it's effects are pretty specific.
But I still would like to have generic +2 armor against everything. To do that, I'm going to be flexible with the Imbue school of magic. Let's say that folks with the Imbue school can decide, with proper study, to really get into materials fabrication. In other words, to get +1 armor, you have to magically infuse iron to make it slightly better than steel. You can describe it in any kind of way you want - event an element to fit the bill. Better yet, give it a characteristic color. This makes it easy to spot.
Say, that fellow has chartreuse plate mail.
Egads, he could brush off a cannon shot to the chest!
As always, the devil is in the details. I'll like to start off with a spell having a casting time of a round, a duration of three or four rounds, range about 5 feet, one target, one molar of material, and maybe a five foot radius of effect and 1d6 damage. Let's see where that gets us, shall we?
BTW spells like wish and limited wish may be special cases. I could go the Hitchhiker's Guide route and say that wish spells are IMBUE PROBABILITY, but figuring out 1d6 effect for probability can get tricky. Maybe you could say that a wish is an essence, but that still leaves you with figuring out 1d6 effect.
I think Illusion spells are limited forms of create. In other words, Illusion Badger creates the illusion that the target has been transformed into a badger.
Anyway, let's see how this idea goes.