In my opinion, the rules don't cover inventing spells nearly as much as they should have.
Also, I think that there's too much of the game focused on life-or-death situations- that is, there are too many Fireballs, and Lightning Bolts, and Slay Livings, and all sorts of those. The entire game is battle-oriented by nature. What if you just want to have fun, and not go around killing things? Whatever happened to all of the good spells like Sneeze? Why are there no spells that help with everyday activities? Clerics have plenty of things to let them raise the dead and destroy undead, but what about baptisms? Why are the Craft and Profession rules ignored as much as they are? Everything in the game that has to do with everyday, non-combat-oriented actions are summed up in 0- or 1st- level spells, and then there's hundreds more spells in the game that have to do with killing people. The game, as it is, is designed for hack-and-slash, for the most part.