Meaningful choices aren't simple. Simple good.
Therefore we should have just one class...
The Wizard. Because it's the only class that's apparently untouchable.
I guess I would be ok with a game that was only Wizards and I can't imagine any other class that could make this lift. We would need subclasses that probe the other thematic elements of the other classes.
I think this would clearly redefine the game and the role of PCs in it.
Right now there is a lot of friction caused on message boards by the fact that supernatural, magical PCs can break the laws of Physics and are at certain levels more powerful than PCs who can't bend or outright break science. This could potentially alleviate that friction.
While this would better achieve balance it also would reduce choice and that is not something I favor. Players should be presented with choices. It should be made explicitly clear that all choices are not equal in terms of power and then players should choose the PC they want to play.