Just an idea I've had. I'm not sure if it would be beneficial enough to the server to be worth adding, but I guess now would be as good of a time as any to share it.
Maybe we could get a plugin than allows staff to disable certain items for individual players for X amount of time? This wouldn't just apply solely to eggs/snowballs/potions, but perhaps also TNT/Lava/Flint&Steel. If a player is abusing these, or other items, they may have those items disabled temporarily.
It seems as though snowballs and eggs were a constantly recurring issue in creative. I can only see this problem becoming worse with the addition of status-affecting potions. It's true that it typically only takes 1 temp-ban for a player to stop spamming thrown items, but perhaps temporarily disabling the items would be more effective. It may also be a way for donors/veterans to handle these situations when no mods are online. This would essentially force a player to go and do something more constructive, by allowing them to remain in the game, but be unable to continue antagonizing another player with projectiles.
Again, it's only a theory. I have no idea how coding these things works, and I understand it may be too much of a hassle to be worth implementing. I just figured I'd bring it to the table.