Medicine and dangerous liquids would be a very cool addition. As the other people postes here said, there would be many cool things you could do.
For example, a hospital with high-tech devices and so on would be cool, or a secret base were chemically things are developed.
As well, much things in minecraft have an industrial conterpart, so why dont give brewing another one. That would also be a chance for some new plants, and maybe even some multiblock devices.