1.A /convert command which when put in the cords for a block it will CONVERT it into a falling block.

2.A selector for the /fill command EX:/fill ~3 ~3 ~3 ~-3 ~-3 ~-3 packed_ice 0 replace !Air
this will replace all. blocks but air with packed ice

3.The ability to add certain tags to players with entitydata

that is all for now please tell me what you think of these three