What it says on the can - either buff living pickaxe to diamond level, or add a config to let server owner decide what level it should be. Currently there is next to no incentive to craft it, since the only benefit of living toolset (aka inbuild regeneration) is only useful to have on tools that you are planning to stick with long term, as it eliminates the problem with rising upkeep. But for iron tools there is no need to preserve them since 1 - iron is almost as common as dirt and 2 - iron tools only usage is to mine 3 diamonds for the diamond pick, after which you'll never go back to iron tier again.