In many of my projects, the Chemist class may have certain unique traits when it comes to Item use. Some include:
-2x effectiveness of Items
-Items are not consumed upon use (Items made as Skills, rather than default Items command)
-Efficacy reversal (as mentioned, Antidote applies Poison, Potion deals DMG instead of Healing, etc.)
-"MIND" Stat is linked to Items effectiveness, higher MIND = Higher heals. Higher MIND = Higher status heal (Stun, Numb, & Paralyze, 3 tiers.. Higher MIND heals higher tiers)
-Can "Mix" general herbs/materials to made Potions/Bombs.. etc.
-Natural Job progression leads to [Alchemist], who's Items now have a Magical attribute added (Think Potion heals HP used by Chemist. Potion used by Alchemist heals HP & MP).. (Also, A "bomb" now can be an "Ice Bomb" or a "Bolt Bomb")
In one of my projects, Chemists are the ONLY Job Class that can use Items in battle. Outside of battle items can still be accessed via menu though. My justification for this is that in the fray of a fight, a Chemist can quickly analyze what Potions are which, when not in battle, anybody can slowly "read the labels".
However, in THIS particular project, there are a wide a varied means of healing, so Items are not REQUIRED. They are, however, the most effective (Can't miss, can't be muted, always an absolute value) means of healing and status management.
One project to the next, Job Class balance and Stat balance will flow and vary. That's the key to keeping it fun and fair. Personally, I never, ever, ever, EVER, make a project with "Subclass"es that can be modified. That's just too much for my brain to process. I also tend to keep very small algorithms and damage formulae.. I find it more challenging and engaging for the player to not have to spam attacks or ultra skills. I also usually don't include traditional "Levels" in most of my projects.. start to finish I like to make every battle challenging, but fair, so the player learns what works best strategically, rather than grinding to overpower the foes. It just doesn't make sense to me how one village is surrounded by Slimes.. and then the next village is surrounded by Harpies.. do the NPC's in the town surrounded by Harpies all have to be Level 15 before they buy a house there??? Hehe.