I was transporting lava the other day and was just thinking how it'd be useful to be able to stack buckets and other items (doors, signs, ect) that just fill up space in your inventory during building projects. There are several plugins that allow the modification and honestly, I'd kill to even be able to stack 16 buckets... maybe maim for stacks of 4.

You say you'd kill, eh? Heres a trick that works for me- First put any items you don't want to lose away, and make sure your ok with losing some exp. Warp to your home location, then use /killme. Then when you respawn, walk or warp to a location where you can access the /home command. Sometimes it will lump together signs, buckets and other unstackable items you drop. Give it a shot <object class="emojione" data="https://resources.enjin.com/1489581540/themes/core/images/emojione/svg/1f609.svg?0" type="image/svg+xml" standby=";)">;)</object>

Edit- Heres a screenshot for proof.

You can stack them by putting them into a shop, then taking them out. The output will be stacked buckets. It can be used for most any un-stackable items.