I'll attempt. Here ya go I tested and everything a config is made to set the cooldown. https://www.dropbox.com/s/229duwmrok6kjc8/DispenserCooldown.jar EDIT by Moderator: merged posts, please use the edit button instead of double posting.
Maybe with command /somecommand cooldown <secounds> and then rightclick the dispenser ( If that is possible). Maybe permissions for that...I hope that will not conflict with other dispensers
Done if you have any errors just say. The command is /dispensercooldown [seconds] https://www.dropbox.com/s/229duwmrok6kjc8/DispenserCooldown.jar
Maybe you can also add message. Example when i used dispenser and there are example 10 secounds interval and i am turning dispenser on after 2 secounds it says You have to wait 8 secounds again to use this dispenser. Is that is possible? Sorry for bad english