I remember J.E. Sawyer had really good thoughts on feats vs. classes. Iirc he thought that prestige classes and multi classing in general was a needlessly rigid system as opposed to just giving the player freedom to choose feats that give new abilities. Start off as a rogue, you get a select number of feats and emphasis on certain rogue-y skills, and then if you want to add arcane spellcasting just choose corresponding feat for your character. Works out a lot better than multiclassing IMO.
