My idea for fixing this lack of balance is providing some incentives for going the pure class route. Now, it could be argued that taking a pure class route should be more difficult, and that it is a good test of self-discipline, and that providing incentives for it would negate those entirely. Oblivion's enemy scaling system, in my opinion, made it excessively cumbersome to take a pure class route once a sufficiently high level had been reached, which I think breaks those arguments, but then again, it has been recently announced that http://www.gamesas.com/index.php?/topic/1156332-is-level-scaling-backnoooooooooooo/page__st__40__p__16933097#entry16933097. Even if it isn't as difficult to take a pure class route in Skyrim, I think it would still be beneficial to the game to add significant incentives for it. Those who prefer generalization (the large majority) don't lose out at all, as this playstyle is not disincentivized at all (other than losing out on the incentives for playing 'purely').
Here's a summary of my arguments.
1. In Morrowind and Oblivion, class purity was heavily disincentivized, while class generalization was highly incentivized. I'm presuming that the system in Skyrim will be similar enough to make this statement true for it as well.
2. To solve this, compelling incentives (e.g. special perks) should be provided for going the pure class route, so that there is some sort of reward for it. There is no need for a penalty to be inflicted upon generalization playstyles, though.
So what do you think? I've made a poll for this purpose, but I'm also hoping that people will introduce new arguments, information, etc. in replies.