Come to think of it, we could have some REALLY good Metroid style levels in MM2. Think about it:
Screen locking means that players can't accidentaly trigger some event, as well as freeing up space for more blocks
Dry Bones Shell can make traversing Lava Areas more dynamic
Required objectives mean that players can't cheese the level just skip the final boss
Keys and Locks can make the other bosses required to get the powerups
Checkpoints can serve as save rooms that grant the players all the items they collected to that point
The night theme could serve some purpose in some cases