I propose that some new elements are implemented that cannot be directly placed, but must be created like RIME and FOG (ignoring the secret menu). I can't really think of a real use for it, I just thought it'd be nice to be able build useful refineries and stuff or mix two elements into something else.
Still, the idea is a sound one. It's fine for there to be some, which are needed for state changes, such as dead yeast, but I wouldn't want things to go overboard with alot of elements being 'hidden' or unselectable.