Well you can already do it, so you basically have unlimited oils (which is ridicules)..
Wouldn't mind it if, as others have said, that Geralt applies it ingame Witcher 1 style, that way it kinda maybe balances out the fact that it never runs out.
Also in regards to potions if it was limited to only using the consumable slots in combat, but then added an upgrade-able 'pockets' like saddlebags. So you start out with the 2 slots, but maybe you can end up with 4 potion slots and 3 bomb slots or something along those lines, so you have to prepare but you can add more to your pockets so you aren't so limited.
Wouldn't mind it if, as others have said, that Geralt applies it ingame Witcher 1 style, that way it kinda maybe balances out the fact that it never runs out.
Also in regards to potions if it was limited to only using the consumable slots in combat, but then added an upgrade-able 'pockets' like saddlebags. So you start out with the 2 slots, but maybe you can end up with 4 potion slots and 3 bomb slots or something along those lines, so you have to prepare but you can add more to your pockets so you aren't so limited.