You can turn pistons into just piston heads or piston bodies by utilizing worldedit (//wand for the wand). You power the piston and remove either the head or body depending on what you want. You can also do this with the door, creating a half door.
To use the wand to remove blocks, type //wand to get the wand into your inventory, and left-click and right-click the block(s) you want to edit. From there you can use //set 0 to replace the block selected with air.
Just be warned, any block updates next to the blocks you've "glitched" will make the piston head/body and half door disappear, so be careful!
I hope this helped <3