I would like working doors. I know that there are garage doors that can open and close in H2A's forge, but they don't fit in too well with the rest of the forge palette. Just a regular door that slides horizontally/vertically.
Also, the ability to have pieces move around and rotate. For example, have a block move in a pattern so that maps can have lots of blocks constantly in motion-sort of like the windmill on Zanzibar.