We have a 20th level magicican in a shadow world setting that has 17 named lists all of them to 20th level and a couple to 25th.
We also have a 15th level Illusionist with 22 lists to 10th and 3 lists to 20th as a comparison. If anyone has taken a 'individual spells' style magic user to thos sorts of levels it would be interesting to see how they compared. This weekend the Illusionist used spells from:
Summoning, Spell Enhancement, Guises, Illusion Mastery, Light Moulding, Lofty Bridge, Invisible Ways, Essence Perceptions, Unbaring Ways, Detecting Ways, Rune Mastery, Living Change and Delving Ways. In addition spells from the Smell, Taste, Feel list were prepped but not actually cast.
That session included a single, fairly non-violent sneak in, sneak out raid on an enemy stonghold.
If the individual spell purchases are really limited to realistically 4 or so a level, that illusionist would ony have in the order of 60+ spells. I don't think he would have been able to to half of what he achieved. I am more in Dark M's camp of the PCs should be the heroes of the world.