I was googling something unrelated and stumbled across this nice Carjacked Seraphim post called Spontaneous Wizard Magic. Spontaneous clerical casting was introduced in 3E, if I recall correctly. The idea was that you didn't need to load up all your spell slots with various cure wounds spells. Instead, you could burn off any memorized spell and turn it into dice of heal.
Jim at Carjacked Seraphim nicely applies that logic to magic-users. I think he is writing for 5e, but I actually think his concept would work at least as well for old editions. Assuming you don't mind the raw power this gives MUs. I'm kinda mulling over how it would work in a Basic/Expert game where the hard spell book limits were enforced. I.e. a second level MU could have at max two first level spells in his book, but if he was, say, an enchanter, he could turn any spell into Charm Person on the fly, whether he had that spell in his book or not.
|Now you jerks will really fear my wrath!|