Dang...
Since when is "Arcade mode", "serious mode"?
And since when is "Career/Simulation", "easy mode"?
(These are not my personal words, but this is exactly my view on this part of the issue)
"Both can be challenging and fun, but arcade games tend to have an easier learning curve. It can be challenging, but allows either a casual gamer or a novice to jump in and be quick while a true sim requires practice and has a steeper learning curve. A true sim is going be a game that you can’t just jump in and go fast and win. An arcade game is a bit of a level playing field."
So this whole idea of "Anyone should be able to finish Careermode" is just the wrong way of thinking.
Arcade should be easy, Simulation should be hard. Not the other way around.