This works mostly as the spell-based magic system in the Basic Set 4e and GURPS Magic for 4e, with the following exceptions:
- Spells do not normally have other spells as prerequisites, and by default do not have prerequisites at all. Optionally, Magery prerequisites and other non-spell prerequisites might remain (e.g. Simple Illusion might still require the caster to be able to see, and/or to have IQ 11 or higher, or Recover Energy could till require Magery 1). Optionally, Very Hard spells might have one or two Hard spells as prerequisites (e.g. Enchant having 'either Temporary Enchantment or Scroll' as a prerequisite).
- Spells may default from other, similar spells at smallish penalties (e.g. Explosive Fireball defaults to Fireball-2), or from appropriate College skills (which should be Very Hard) at -6, or -7 for Very Hard spells. Optionally, the spells from the basic set (pp243-253 & 480-481, or perhaps only the ones from pp243-253) can also default from Occultism at -8, or -9 for VH spells.
The Charms perk is still useful, as it allows you to instinctively know a spell without having other means to learn it; Shortcut to Power makes rather less sense, though, and thus might not exist.
Thoughts?