I made this chart because I'm trying to figure something out. I have two contradictory impulses when it comes to rules for Magic-Users.
1) I like the simplicity of "Here's your list of spells known, pick 2 from column A and one from column B that you have ready to go."
2) I also enjoy seeing magic-users track down ancient tomes to try to glean new spells from them, wrenching every last iota of power from those faded glyphs and obscure charts.
Anyhoo, step 3 above is the basic mechanic of the Vancian system. Step 2 often ends up working via fiat in my experience, unless your DM actually uses the "% Chance to Know" chart from 1st edition AD&D/Holmes Basic/Supp 1 Greyhawk. I like the idea behind the % to Know chart, but the implementation is dry and sparse. Step 1 and Step 2 have a pretty interesting implementation in Call of Cthulhu that might be worth ripping off.
"Man, is there anything Jeff CAN'T do when it comes to gaming? This guy is like a critical 20 every roll. Jeff can bite the heads offa five game geeks, including their sorry-ass DM, and spit 'em into a large duffel bag ONE AT A TIME!...that's just the kind of messed up bastard he is! You think yer a gamer, punk? Well..do ya? Jeff will depants your weasel-ass right in front of your grandma."