It would be as if you have all the abilities of your current class and can pick out traits from other classes you've played. Almost allocating points to them like the blue mage in FFXI.
Someone else on here said it, and it made perfect sense... However we don't know for sure if it will be used in that way.
If that is the case, I still hope that there isn't a certain class that uses dual wield and we have to waste a slot (or points) on it. I always thought it was BS that ninjas were the only dual wielding job. Could be cause I personally didn't care for the job, but it would have just made sense for other jobs to, you know, use their other hand.
The more I train, the harder I get. The harder I get, the more lethal I am. The more lethal I am, the fewer opponents. The fewer opponents, the less to lose. The less to lose, the more I let up. The more I let up, the more room for mistakes. The more room for mistakes, the more I train.