Something that i found not really realistic is the use of barrels for fermentation. Usually fermentation is done in open vessels (for beer, tequila etc). Barrels are mostly used for ageing (not a specialist so correct me if i'm wrong). The fermentation mechanics could be changed in this way by adding fermentation vessels, and a new tags "aged", "double aged"...Associated with the use of barrels. Extention of potion effects could be obtained by "ageing" instead of adding redstone. Distillation could also replace the use of glowstone, and distilled beverages could also be aged.

We will need to discuss this internally. Normally you would use a glass carboy or fermentation bucket, or large scale is a conical fermenter. It is rarely done in an open vessel as that introduces foreign contamination which will make it a sour.

The challenge is making it realistic while not too cumbersome.

Thanks for considering! I was thinking more about medieval times were natural fermentation in open large wooden vessels was maybe more common. Also I watched recently an HTME episode about tequila with open fermentation: https://www.youtube.com/watch?v=Uyj6e-Z8hBw . But maybe this is something specific to distilled beverages. Also I started coding an extension for growthcraft adding rhum and sugar extraction from pressed sugarcanes (just for fun, i'm not planning to release anything). I was thinking about how to implement distillation, and this is how i though about this fermenting/ageing/distilling mechanics.

Well this mod might seem medieval at the moment but it will no longer be after chocolate and such is considered.
Anyways i like the aging and distillation idea since i think the additional effect boost should be a reward for time not some magic minerals