I think it would be awesome to add in really powerful acids that could dissolve virtually anything, but only in set quantities (e.g. X blocks of acid dissolves Y blocks of other things and the acid is used up in the process). I can think of three ways to do it: 1) Add two new inert liquids that behave like water until they come into contact, transforming them into acid. 2) Same as 1, but only one new liquid that would react with water. 3) add a new stone type that transforms into acid when it touches water.
The idea would be for acid to dissolve virtually everything, including stone, with maybe the exception of candy. You could weaponize it, use it for rapid mining/cave exploration, or good old fashioned FUN! It could be the most dangerous thing since magma. Does this sound feasible/like a good idea?