In short, my suggestion is to extend the definition of griefing to include the destruction of non LWC boxes for the sole purpose of leaving items to decay.
At present, griefing only applies to placed blocks, but when you have a couple boxes of cobble, stone, and gravel from excavation (or whatnot) that are destroyed (but the boxes are placed back), its clear the purpose was none other than than to have the items decay.
I understand that enforcing this might be thought to be difficult, since differentiating between stealing a chest of dirt vs leaving it to decay might be difficult after the fact, but in cases where an unreasonable number of stacks of items are all "gone" at once (especially of otherwise worthless material as was the case for me), mods can readily identify that as intentional grief.
At present, griefing only applies to placed blocks, but when you have a couple boxes of cobble, stone, and gravel from excavation (or whatnot) that are destroyed (but the boxes are placed back), its clear the purpose was none other than than to have the items decay.
I understand that enforcing this might be thought to be difficult, since differentiating between stealing a chest of dirt vs leaving it to decay might be difficult after the fact, but in cases where an unreasonable number of stacks of items are all "gone" at once (especially of otherwise worthless material as was the case for me), mods can readily identify that as intentional grief.