I think there wouldn't be any problems for letting players to have max level for all classes, as long as there's a cap on the physical level, that means players will have a limited amount of AP, so they can only use certain numbers of abilities/weapon skills at a time.
As for crafters, since they're now treating them as an individual class, not like a profession as in XI, I'm assuming there will be something different. Maybe they'll have a system that you can level up all of the crafter classes, but you can only master at one (you can decide which one to master anytime in the game), and for every crafting class, there're two type of recipes, regular recipes and master recipes. Everyone can learn the regular recipes, but only masters can learn the master recipes. Let's take cooking for example, at level 1~5, you can make 5 dishes with regular recipes, and the most HP or MP restored maybe 50, but for master recipes, there maybe an extra 2 dishes you can make, and the food can restore 70 HP or MP and so on.