Should be part of the base game in my opinion.

Exactly! Thanks for using :)

for those who may be interested
I've noticed that this mod does not work with IR2 (Industrial Revolution 2) or that IR2 overrides it somehow, as it requires its own technology to unlock barrels and barreling.
I did not get any error and game is working fine when I create new world, but all barrels are still locked under IR2 "Advanced Fluid handling" tech

I've checked IR2 and I think there is no need to make any changes. It's a fairly complicated mod already, and there is no way for me to consistently replicate the mod's effect.

IR2 unlocks barrel items only in "Advanced fluid handling" technology which is further down in the technology tree than techs that unlock liquids themselves (Iron Milestone unlocks pumps, thus water; Oil Processing unlocks oils, petrol and lubricant).

The only exception is sulfur, which is in another branch of the tech tree than barrels, but I can't change it in a vanilla way without adding some new tech - modding API makes technologies declare a list of unlocked recipes, and doesn't support an item declaring a list of technologies. This makes it impossible to make sulfur barreling recipes be unlocked after both "sulfur processing" and "advanced fluid handling" without introducing a new tech that depends on those two and unlocks the barreling recipe. I don't want to create custom techs myself, so I'll leave it as is.