Here's a silly idea that could be used creatively, Jump Pads! They launch you into the air a few blocks, they can be configured, or even set to launch you at an angle. Imagine the possibility's! PVP arenas that have you bouncing around... Dungeons that play like a platformers... Just imagine it, I think it would be perfectly valid to sell these for plat, but sadly that means I wont get to buy them, since I don't got plat, but that's aside the point. Anyway, sob stories aside, Jump-Pads should be added.
Just for an example, if we did have jump-pads that we could angle, we could recreate quake maps as PVP arenas.