I think this is a good idea - levelling a crafting class to 15 doesn't take much time or effort, it makes sense from a lore point of view, and for those people not focused on crafting it means they don't have the pain of getting to 30 (which is much harder and more expensive).

Perhaps this could start as an 'apothocary' class, that specialises in using skills for placed/thrown/effect skills. Kinda like using items, but without the actual item usage part (just using a skill instead). SE have already said they didn't want any class relying on items (such as rogue/ninja with thrown items), so skills that behave like thrown concoctions (AOE explosion, knockback pulse, buffs, debuffs, DoTs, HoTs, etc). The job for Apothocary could then be Chemist, growing on the item-based skills with 'mixes' as job abilities - similar to the ninja's ninjitsu though perhaps with more healing/buffing benefits over damaging attacks

I can see some real merit in a chemist within FFXIV :-)