Evaporate used to be a spell that "threw" potions. It was overpowered, so now it's not a spell any more.
This is something that is a good example of choices being removed and losing tactical play. And it wouldn't be impossible to balance.
"New" Spell, Evaporate.
Fling a small quantity of magically enhanced potions at your foes, causing either a cloud of gas or the direct infliction of ailments. Level 2 spell.
Mechanics.
Choose between 1 and (size based number) potions to throw. For each potion chosen, increase the radius of the potential landings by one. So, for example, throwing a single potion will always hit where you aim. Throwing 2 potions will have a cross shaped landing area. Three would have a fireball shaped one, and so on. However, this doesn't mean that the cloud fills the area. Each square in that landing area would have a chance to be hit by a potion, and either cause a cloud, or if there is a foe there, directly inflict the ailment onto it without making a cloud. The chance to hit a foe would be standard for most magical spells, and if it misses it rerolls to see where it makes a cloud. Clouds would linger, block LOS, but have reduced damage or effects based on the sort of cloud.
The effects would be similar to the old clouds. Steam would be dropped to be about halfway in power between magic dart and the level 2 attack conjurations on a direct hit, about the same power as magic dart as a cloud. The poison and confusion clouds would have about a half chance to inflict their ailment on a foe as a cloud, and if it hit, would inflict it.
So, if you need to hit something, you throw a single potion at it. If there is a crowd, you start flinging potions like mad to try to block LoS and maybe inflict some confusion or such. Actual damage output would be lower then other level 2 spells due to increased versatility.
Oh, and the size thing is to make it less attractive to Spriggans. Fulsome Distillation was interesting for them as it effectively allowed them to eat clean corpses. Spriggans would be able to throw one at a time, maybe 2, whereas a troll could fling 6-10 potions. Note, yes this is meant to be in the turn.