I think there is a lack of invisible blocks in PB.
I had some ideas that could make PB more usable for some people (like me):
*IB means: Invisible Block
Light source IB: As the fire does but without the player have to see it
Bouncing IB: Makes a tile solid and also you can bounce in it or something like that.
Item IB: Place an item in there, and the player will not be able to see the item, but when pass through it, the player will receive the item and the effects will be saw.
Checkpoint IB: As the checkpoint does, but in invisible and the player can handle if have a message of checkpoint or will be automatic and the player can't know if had passed a CP.
Place more ideas below here