I still don't understand why we need to touch their book learning at all. Right now elementalists aren't played mainly because wizards are so good. The solution there isn't to make elementalists worse.
Right now, there is a case to be made for playing elementalists over wizards: They have better access to spells in the early game, before the books you want or need are abundant, and so have a more consistent and overall easier early game. While they taper off mid- to late game compared to wizards, they're still extremely powerful by virtue of being spellcasters - more powerful than most other classes in the game. Combine the easier early game and the still amazing mid- to late game, and there is plenty of reason to play an elementalist over a wizard.
The more I read these debates, the more I get the sense that comparing everything under the sun to wizards is where the problems begin. It's not really the fault of elementalists or druids for that matter that, when evaluating a class, our mouths start to water as we imagine ourselves standing in the midst of hordes of foes acid balling them until our fingertips dissolve. Wizards are just about the only spellcasting class that can flaunt their overabundant magic power in this manner, it's true. (At least, with that amount of ease. Other classes can find ball spellbooks and get decent amounts of castings. 400 Fireball, incidentally, is more than decent.) But that doesn't make either elementalists, necromancers, priests or even druids obsolete. They can still read. They still learn spells. They will still have great repertoires come late game. It doesn't distinguish them from other spellcasting classes or from wizards - but it's no less an essential part of what makes them fun or worthwhile to play. Take spellbooks away from them and you have to absolutely bend over backwards developing alternate features and super special awesome class powers to have a hope of preventing them from booking their ticket to obsolescence, something Thomas can't really afford to do this late in development. Mindcrafters are not very widely used and also arguably inferior to proper spellcasters (including druids), but they still have some appeal because some mindcraft does things spells cannot.