Libramarian
Adventurer
There is a conflict that is readily apparent. The more resources the PCs potentially have to turn an overwhelming encounter into a beatable one, the less predictably overwhelming the encounter is. As variability in PC encounter performance goes up, predictability of encounter difficulty (i.e. balance, in this sense) goes down.A balanced system doesn't keep you from creating an overwhelming encounter, nor keep players from finding a way of making it less overwhelming. It just makes pegging an encounter at 'overwhelming' a good deal easier and more consistent.
Now, judging from the rest of your post you seem to have the prototypical preference for Harlem Globetrotters-style, Right to Dream CAS, where "balance" in the PC-Encounter relationship doesn't mean that each side has a fair shot at winning (this is important) -- it means the PCs will almost certainly win. So they get to choose their abilities based on their character concept, rather than being "forced" to optimize.
Just like in a Globetrotters game, where they get to choreograph their moves based on whatever looks most entertaining, because they know they're going to win anyways. They have the "right" to put on a show, rather than being "forced" to gameplan to win.
But on the other hand, somebody who is actually looking for a competitive bite to the proceedings won't be satisfied with this. They want to be forced to gameplan to win, because if they do win, that's a compliment on their skill as a player. They like optimizing their build and spell selection on a rules-heavy level, or rubbing mud on their body to avoid bees on a rules-light level, because that makes victory feel sweeter and well-earned. Even if they had to sacrifice their character concept or the serious/gritty tone of the game to get there.
That's the potential conflict between Simulationism (Right to Dream) and Gamism (Step on Up) in a nutshell. And why I, and I think LostSoul, associate 4e-style CAS with Simulationism rather than Gamism.