This plugin will allow your players to "reinforce" any block. So that when other players try to break it, however many times they reinforced it, it takes two extra minutes in between breaking.
So I reinforce a Grass Block two times, a player can break it once, then has to wait 2 minutes to break it again for good.
They can do this to any blocks, even spawn. You're gonna have to work around that, though I'll probably update it later.
Commands
/breakall [This'll let you break any block instantly, immediately deleting all of its reinforcements. Do this command again to return to normal
]