I don't like the idea of lowering memory cost based on the spells respective attribute. It basically removes the mechanic of memory and memory requirements late game which were used to balance certain spells. The balance would no longer be there when you have 3 or 4 points in all the schools you want, giving all spells a 1 memory cost.
Well, that's not necesssarily true. The ability point distribution of course should cater to the experience which means that you maybe should get less ability points while leveling up. Imo you shouldn't be able to master two or more schools before very late in the game. Or at least not without sacrificing everything else in terms of character development.
And of course the balance is still there. You seem to forget that high level skills still have high AP costs and high cooldown times. So even if you have a huge range of spells at your disposal you probably can't use many of them more than once in combat.
The high and very rigid memory requirements that our currently implemented only severly limited the range of spells you can use in combat which imo reduces the fun of combat because you have less flexibility and a much smaller range of possibilites to adapt to your enemy. Lowering memory requirements once you level up in a school would give you real and tangible benefit for leveling up. It's pretty disappointing if you put another ability point in a school just to notice that you can't really use any of your new skills because your memory limit is still full. That takes a lot away from the enjoyment of getting stronger and leveling up. Leveling up should really make you stronger and should enhance your arsenal. Balancing (I only speak for SP here!) should be the result of multiple factors: memory requirements, AP costs, cooldown times, source point requirements and the price for spellbooks. Right now the memory requirement dominates the rest and is imo way too rigid and strong. Mid-level skills with a three slot memory requirement are hardly worth to be taken into your deck since they severly reduce your arsenal while still having high AP costs, high cooldown rates and source point requirements on top. It even goes that far that your wizard can come into situations in combat in which he has no ready spell at all during a turn because he has only very few low-level skills and his one or two high-level skills are still in cooldown. On top of that it's kind of boring to use the very same spells all the time because your arsenal is so small. That just doesn't sit right with me. Reducing the rigid memory requirements for level up in a certain school would imo soften that issue and would actually encourage people to level up and enjoy the new spells and skills they have at their disposal.