Just a suggestion of improvement:
Could you, please, make dispensers to be placed with face down or up.
This is realy needed for:
1)Different traps
2)Spawning mobs from below of the ground. (Example:zombies comming from the grave. If we place block above the dispecer and nearest blocks, zombie will spawn inside the ground and slowly dying, so we need up-faced dispencer. Another example: spider, jumping from the ceiling - here we need down-faced dicpencer).
Please, just think about it.