The main problem with requiring skill checks, of course, is that skill checks are so easy to boost in 3e, and a secondary problem is that if you're basing the DC on spell level it goes up by a different rate than Spellcraft ranks based on whether it's using ranks, 2*ranks, or whatever (i.e. the Truenamer problem).
One variation on the prerequisites idea that I liked, tried by one of the DMs in my group, was the following, spoilered for the tangent:
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Each spell requires a DC 15 + 5*spell level Spellcraft check to learn it, but each spell has one thematically-related prerequisite spell per spell level. Each of those prerequisite spells that you already know reduces the DC by 2 (so a 9th level spell has 9 prereqs and knowing all 9 reduces the DC from a near-impossible 60 to a manageable 42), and if you fail the check for a given spell you can retry the roll each time you learn one of the prerequisites. Additionally, specialists take a -4 Spellcraft penalty for spells outside their school and generalists take a -8 penalty on checks to learn spells of any school, each school has a different associated Knowledge for the Spellcraft synergy bonus (Kn:Planes for Conjuration, Kn:Religion for Necromancy, etc.), and of course prevent any magical enhancements to the skill check like +30 Spellcraft items or guidance of the avatar or whatever from applying because the Laws of Magic are a jerk like that.
A 1st level wizard with max Spellcraft and +2 Int would need to roll a 12 to learn a 1st level spell of his specialty school while only an 18 Int generalist could even have a chance to pick up 1st level spells at 1st level; a 20th level generalist wizard with +10 Int, 5 ranks in the appropriate Knowledge, and max Spellcraft can roll at most 47 on that Spellcraft check, making it practically impossible to learn a spell without almost all of its prereqs, while if he were a specialist he'd need only 1 or 2 prereqs from his specialty school.
That system is probably more complex and less friendly to generalists than most people would want, but I think it does a nice job of encouraging thematic spell groupings while being forgiving of players who want a more eclectic spell selection.
Originally Posted by PairO'Dice Lost
The main problem with requiring skill checks, of course, is that skill checks are so easy to boost in 3e, and a secondary problem is that if you're basing the DC on spell level it goes up by a different rate than Spellcraft ranks based on whether it's using ranks, 2*ranks, or whatever (i.e. the Truenamer problem).
Re: D&D 5th Editon Discussion: 6th thread and counting
I like it, it's interesting. Definitely restricts casters more.