The Shadow
Hero
I like some of your ideas. I think Spells & Powers, from the 2e "skills & powers" ruleset (2.5?) had this as an alternate magic system.
I seem to recall something like that, from the misty days of yore. I think it was a bit more complicated, though. And certainly nobody ever accused 'Skills and Powers' of being well thought-out or balanced!
Some concerns: It might not satisfy some people, because "it's not D&D".
Yes... I know. So does WotC. That's why I said it was a crazy idea that had no real chance.
That aside... you need to careful balance things. You can't simply translate the things from current table and call it a day. This way, you make Wizards quite more powerful than they were with the other system. I know any 18th level wizard will happily trade 5 level 1 and 2 level 2 spells to get another Time Stop. This does not mean the system can´t work, just that you need to balance it with the idea that, at higher levels, low level spells are going to be recycled into higher level spells.
Yeah, I know that too. Right now, I'm favoring costing each spell as the caster-level at which it becomes castable. So Time Stop would be the equivalent of 17 1st level spells. (Honestly, Time Stop is SO overwhelmingly broken, I'm really not sure it can be saved.)
Some people have suggested each spell having its own cost. This seems to me rather burdensome to remember, but it could certainly be made to work. Maybe Time Stop needs to cost 100 spell points or something.