I'm not a fan of a system that allows you to use skills from another class with minuscule penalty. The vast majority of people are not creative or have enough self control not to make a jack-of-all-trades, master-of-all-trades class. Props to you if you want to have a bowman who can cure people occasionally, but if given the option, people will make a class that does everything (see: Elder Scrolls series).

I would be okay if the system limited to choosing between only 1 or 2 additional classes from which you can pull skills from.