This is a bit of a difficult topic. If we're allowed to level all of our battle and magic classes to cap, why, theoretically, can we not level all of our crafts to cap if the crafting portion of the game is supposed to be on par with the battle classes so to speak.

I completely understand the problem of every player potentially being able to craft every item, and think it may very well need to be addressed. I don't think limiting the level progression of crafts is the right avenue, though. The idea of "specialization" where you would pick one of your crafts and gain some sort of add-on abilities to make it surpass your others might be nice.

I also think, though, that re-working crafting to have recipes that are not automatically known on level up and instead must be learned from npcs, quests, or even boss or dungeon drops can help separate crafters from one another. Not every 50 Alchemist would be a carbon copy of one another at this point, and would require more in-depth dedication to one's craft.